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CAPÍTULO 6 -- PROPRIEDADES ACÚSTICAS DE INSTRUMENTOS DA MESMA FAMÍLIA |
There are no writings or documents telling us for certain where string instruments came from, like all of the four traditional families, they descended from prehistory. Most likely a caveman, perhaps an inhabitant of the Iron Age found that by taking his bow, resting it against a hollow log or other chamber, and plucking it produced an interesting sound. After a while someone discovered that by doing certain things, the pitch could be varied.
Thousands of years later, the string instruments we currently use have all of the same basic characteristics as the primitive version. Modern string instruments are very sophisticated and complex machines that vibrate the air in very controlled and pleasing patterns.
The instruments that we lump into today's string family have three basic characteristics in common.
A vibrating string sounds at a particular pitch due to three independent factors; length, tension, and density (roughly translating to thickness).
Each of the above changes assume that the other two factors remain constant in each situation.
Most of the string instruments use combinations of length and density to produce their different pitches. Fingered instruments (the violin and guitar are examples) will use the length factor a bit more--when the musician presses a string down to the fingerboard, he is basically stopping a segment of the string from vibrating. In effect, he is shortening it, and the pitch will go up. Again, the shorter the string, the higher the pitch.
The guitar is the only one of the common strings that uses a change in tension to change the vibrating frequency of the string, and then it usually happens only when the player bends the pitch or creates vibrato.
On most instruments the string is suspended between two structures called the bridge (which is on the lower end of the body) and the nut (which is at the top of the fingerboard).
On bowed string instruments a little wooden rod called a soundpost transfers vibrations from the top plate of the instrument to the bottom plate. This very complex physical system then spreads more of the primary vibration around the instrument, creating a more complex and efficient vibration. Most string instruments don't have a sound post.
A general rule in strings and musical instruments in general--the larger an instrument, the lower the playing range. High frequency vibrations are actually smaller and closer together in the air even though they don't travel any faster. To play these high notes, an instrument must be able to create very rapidly vibrations. A large instrument is held back by the inertia of its body materials. This is the same principle that causes a heavy pendulum to swing very slowly.
A smaller instrument can create rapid vibrations because its construction lacks the mass that would hinder very rapid movement. There is a trade off in the process, though--the greater mass present within the heavy vibrating body moves more air molecules, creating a greater amplitude, or in other words, a louder sound. This is why an orchestra needs to have many more violins than it does basses to balance each of the sections in loudness.
In most resonating instruments there is an "L-L-L rule", the letters standing for large, loud, and low. Usually unless there are some unusual acoustical factors in play, when an instrument or vibrating object is Large, it will play Loud sounds in a Low range.
In an embarrassment to modern science, the string family reached its technological peak in the late 1600s and early 1700s.The best examples of violins were made in Cremona, Italy by Antonio Stradivari, along with members of the Amati and Guarneri families. For reasons unknown to us, certain important techniques of violin making were never passed on to the next generation of craftsmen. Today, acousticians, physicists, and chemists are struggling to find exactly why these instruments sound so good, create such powerful tones, and enable the players to do so much with them expressively. Stradivari and company made other bowed instruments which were also excellent, but the violins they made still stand out in quality and power.
The violin, viola, cello, and bass are most often played with a bow, which is a length of horsehair coated with rosin and dragged across the strings. This sticky rosin, grabs at the string and allows a note to be sustained. Very rarely will any other instruments use a bow, and then, only for special effects.
The string player has a wide variety of effects at his disposal, including a number of types of bowing and pizzicato (plucking) techniques. These instruments can be also played with mutes which causes a major change in their tone color. Players can use varied vibrato effects, slide from one note to the other, and bow rapidly, an effect known as tremolo.
String players also have the added advantage of not needing to stop and take a breath periodically!
The violin is the most well-known of these instruments. It is bowed or plucked, and is considered to be the instrument which can come the closest to the human voice in its ability to convey emotion. One aspect of its construction that gives modern analysts fits is that it can sound relatively strong overtone frequencies all the way up to 20,000 cps. Along with these high pitches, a good violin will sound loud, but never grating or unpleasant.
The viola is a little larger than the violin and plays in a lower range (remember the L-L-L rule). Because of some complicated acoustical reasons it doesn't have the piercing singing quality of the violin or cello, but its tone can be very beautiful and mysterious. It is often also played pizzicato. Like the violin, it is played with the instrument under the musician's chin.
The violoncello (usually just called the 'cello') is much larger than either the violin and viola. It plays in a rather low range, but it has a very bright tone, brighter than the viola, and is often used for solo work in moderately high ranges. Like the violin and the viola, it can also be plucked, but unlike them, it is NOT played under the chin of the player--it stands on the floor and the player is seated.
The doublebass (often called the string bass, the contrabass, or just 'bass') is the largest of these instruments. The bass is a little different from the other bowed strings in that it descended from an older family called the viol family. The viol family was rather large but died out when the violin family came along. The older strings couldn't handle the power and the flexibility of expression available to the violin family. Today, viols are rarely heard outside of original instrument performances of older music.
The bass is the only one of the bowed instruments to make it big in popular music, mostly jazz. While a rare violinist or viola player can be found in the popular music field, the bass is a staple of many jazz bands. In that context it is usually plucked instead of bowed.
The double bass doesn't make a very good solo instrument because of the weight and range of its sound, but on occasion (and in the hands of the right player), it can do well on an occasional solo. Its size and heavy string tension require a great deal of physical strength from the player.
Unlike the guitar, these four instruments do not have frets. Frets are ridges on the fingerboard that stop a string in precise places, trading expressive flexibility for accuracy in intonation (pitch). Sometimes this is a welcome trade off, especially for teachers who have to listen to beginning string players trying to find the right pitches. . .
The GUITAR (this specifically refers to acoustic classical guitar), has a large resonating box, nylon strings, and in this application is not amplified. It is often identified with Spanish music, although it does very well in other types of musical contexts. For being a relatively quiet and intimate sounding instrument, the classical guitar is surprisingly versatile and capable of very subtle shadings in tone color. Some of the most challenging guitar music can have the performer playing two or three running lines at the same time.
Other versions of the guitar will use steel strings, often played by strumming them. Folk musicians will often use a 12-string version, in which the musician fingers and plays the strings in pairs.
The MANDOLIN is a small instrument, often using double strings. It has a sharp piercing sound, and is often heard in bluegrass or other types of folk music.
The BANJO is commonly heard in bluegrass music, but is also common to certain types of jazz, namely Dixieland. Basically consisting of a neck with drum for a resonating chamber, the banjo's sound is very dry, plucky, and bright sounding. The banjo is only one of two major musical instruments to come from the United States (the other one is the Moog Synthesizer).
The HARP has a silky tone and is never bowed. It has a very beautiful, otherworldly tone. Folklore states that in Heaven, all angels play harps. Having heard a few harp concerts, I'm not going to argue the point. It is virtually impossible to make a harp sound evil or menacing.
It has approximately 48 strings and has a range almost as wide as the piano.
The modern harp has a rather complex internal mechanism. While there are only the strings with the natural [white key] pitches, at its base are a series of pedals. Changing one of them will change every C to a C# or a Cb. Another will change every D to a D# or Db, etc. Harpists must always be moving the positions of the pedals around while they are playing, and composers must keep on their toes and not write any combinations of notes that harpists can't play.
The HARPSICHORD has a keyboard like that of the piano. The strings inside are plucked by quills when a key is pressed. The strings are attached to a soundboard which resonates the vibrations in the air.
The harpsichord didn't have the dynamic flexibility of the piano and began to fall out of popularity in the early 1700s, but it is by no means extinct. Its dry, plucky, antique sound (described by its detractors as "sounding like two skeletons wrestling on a tin roof during a hailstorm") has been the subject of a revival in recent decades.
Other less common members of this family include the the autoharp, the ukulele and many others.
The four bowed strings are the backbone of the orchestra. A string orchestra is the name given to the standard complement of strings without woodwinds, brasses, or percussion instruments. String orchestras have a very smooth and expressive sound. Because of their like construction, all of these bowed strings blend very well with each other (meaning that the highest violin sounds are acoustically very similar to the lowest bass sounds).
The typical, even large orchestra of 1800 contained 12 violins, 4 violas, 4 celli, and two double basses. The typical orchestra at the end of the 1800's would contain as many as 32 violins, 12 violas, 12 celli, 8 basses.
A very popular smaller string ensemble is the STRING QUARTET. There is a lot of music written for this group which consists of 2 violins, 1 viola, 1 cello. String quartet music is often described as more intimate, because, unlike larger ensembles which can belt you over the head with masses of sound, a string quartet is very music like four individual soloists.
As you may remember from earlier notes, there are four basic ranges of the human singing voice. Going from top to bottom, they are the soprano, alto, tenor, and bass.
Roughly corresponding to the human ranges, the violin is the soprano member of its family, the viola plays the alto role, the cello is the tenor, and the bass is. . . the bass. The instruments in a string quartet have ranges that overlap somewhat, allowing on occasion for the violins to be playing lower than the cello lines.
The guitar is capable of a wide range corresponding to soprano through tenor. The harpsichord and harp are capable of playing in any one of the four ranges.
All members of the woodwind family have three things in common: first, wood is an important part of their construction (or in the case of the flute and the piccolo, was at one time); second, the vibration is stimulated and created by the player blowing through the instrument, and third; by the two processes they use to change pitch.
Fundamentally, a woodwind instrument is a tube. There are a couple of ways to make a sound with it. One of them is to tap the tube (you can try this experiment with a cardboard tube). You will hear a specific pitch. Tap it hard, tap it soft and you will hear the same pitch in either case. Why would that be?
Let's review the concept of wavelength. Any time an object creates a periodic disturbance in air, it is basically creating a musical note. The reason we hear a high pitch is that those disturbances are traveling relatively close to each other (remember high pitch=short wavelength). When we hear a low pitch, the disturbances are farther away from each other, causing our eardrums to push in and pull out at a slower rate.
Now, going back to the tube, and hopefully you are a little ahead of the explanation--the tube is a fixed length, and produces an air disturbance related to its length--in other words, the wavelength of the pitch is related to the length of the tube.
Now, what would happen if you were to take a knife and cut six inches from the length of the tube? The tube would produce a shorter wavelength. . . and a higher pitch. These pitches are not just at random--they will be a very predictable function of the length of the tube before and after.
In certain cases (nearly impossible with the cardboard tube, but much easier in the case of a narrower pipe), the air in the tube can be stimulated to produce and sustain that periodic air disturbance. One way to do this is to blow across the edge of one end of the tube. This creates a stimulus vibration which gives a regular push and pull on the air inside the tube--which you remember is a specific length and will produce a pitch of a specific wavelength.
The stimulus vibration creates a phenomenon called a standing wave in the tube. Simply, a standing wave is a periodic wave that more or less "feeds back" onto itself, reinforcing its own vibration, sustaining its sound. In a system that is "tuned", such as in that of a musical instrument, it takes very little outside stimulus to create strong vibrations in the system.
A note of physics here--the tube itself isn't producing the musical note; the air inside the tube is doing the vibrating. The stimulus vibration really isn't an important part of the sound heard--it merely gets the ball rolling.
Back to the idea of a woodwind instrument as a tube: that a tube could create a musical sound was an idea well known in prehistory. But--to create musical sound, it might be nice if the instrument could play more than one pitch! At some point in antiquity, someone got the bright idea of tying together a bunch of tubes of different lengths and playing them one at a time. The ancient Greeks called this instrument the "pipes of pan". The longer tubes played the lower pitches, the shorter ones played higher pitches.
Instrument makers eventually got smart and came up with the idea of using only one tube--but changing the length of air vibrating inside.
This was a little easier than it may initially sound. It was discovered that the tube could have a series of holes drilled in it. When the holes were sealed by the fingers of the player, the air column inside acted as if it were the entire length of the pipe, producing a pitch at that maximum wavelength. When the farthest hole from the stimulus vibration was uncovered, the air column acted as if it had been shortened by that length, produced a shorter wavelength--and a higher pitch. Opening more and more holes progressively shortened the air column, creating shorter wavelengths (again related to the length of the vibrating air) and higher pitches.
If the holes were drilled at the right places, the musician would get a usable series of notes.
Similar to the acoustical principles of the string instruments, you need a very long air column to produce a low pitch. The loudness part of the L-L-L rule doesn't apply here. Anyone who has stood near a piccolo--the smallest instrument in the orchestra--and walked away with ears ringing will be able to verify that.
While the length-changing scheme works very well to change pitches, there is a second procedure that allows these instruments to change pitches--that is to change the standing wave that is vibrating the air column.
In other words, an air column of a fixed length can vibrate at more than one pitch.
This might seem like a contradiction of physical principles, especially in light of the illustration about tapping the cardboard tube in the above paragraphs, but this is only because using the tapping to produce musical sounds isn't an exact model for the actual process taking place when a musical instrument is played.
Let's say we have a tube producing a note with a wavelength of 10 feet (this happens to be the note "A" found in the first space in the bass clef). Conditions exist that allow that same length of tube to produce pitches that have wavelengths that will fit an even number of times into that length of 10 feet. A pitch with a wavelength of five feet can also be sounded (the 5th line "A" in the bass clef). Ditto for pitches with wavelengths of 3 1/3 feet, 2 1/2 feet, 2 feet, etc.
If that pattern of notes looks a bit familiar, it is because you saw it only a few pages earlier--in the section on overtone frequencies. The notes that can be gotten from a pipe correspond exactly to the overtone frequencies made by the lowest one! Again, one more close relationship between mathematics and the sounds produced by musical instruments. When an instrument changes pitch via this method, it is often described as playing the "harmonic series."
In practice, this means that an instrument such as the flute plays its lowest pitch with all of the holes covered. By opening the holes one at a time, the instrument changes pitch. At some point, the flute player will blow a little differently, changing the standing wave in the tube. The earlier open/closed hole combinations will now produce a whole new set of notes. When all of the holes are again open, a third standing wave is used and another set of notes can be gotten from the instrument.
Modern woodwind and most brass instruments change pitch by way of these two processes--changing the length of the air column and changing the standing wave sounding from the tube. Brass instruments tend to use the standing wave changes more than do woodwind instruments, but without one or the other, it would create a severe limitation on what each instrument could do.
While many instruments from other traditional acoustical families blend in with each other very well, the woodwinds are a study in contrasting, even exotic, tone colors.
The strings are bowed or plucked, brasses all consist of a mouthpiece and tubing, and percussion instruments are struck, producing a distinctive sharp attack. Woodwinds are lumped into three categories by their initial sound production--single reeds, double reeds, and edge tones. These three processes help create distinctive timbres.
Single reed instruments use a single vibrating reed (a reed is a piece of cane) attached to a mouthpiece. Blowing across a reed causes it to vibrate, creating the stimulus necessary to vibrate the air column. If you've ever blown across the edge of a blade of grass and made a noise, you have made use of the principle. Modern single reed instruments have only two subfamilies, the clarinet family and the saxophone family.
The most common clarinet has a rather wide range extending from tenor to alto and a good clarinetist can play convincingly in the upper register (soprano range). Usually made of black ebony wood, it has a darkly serious tone, but when played by a good jazz clarinetist, it sounds anything but serious. The bass clarinet is a lower and longer version of the same instrument and has a similar sound. On occasion, an alto or soprano clarinet is used, but the standard Bb clarinet and the bass clarinet are the only ones to have stood the test of time well.
The saxophone family is the newest member of the woodwinds, having been invented in the mid 1800s by Adolph Sax. All other woodwinds date back to the middle ages and beyond. Many different versions of the saxophone exist, playing in many different ranges, including sopranino, soprano, alto, tenor, baritone, and bass, although bass saxophones are rare.
A saxophone can produce a very smooth silky sound, a wailing growl, or any tone in between. Because of intonation problems, they have never become a staple of the symphony orchestra, but have made up for it by becoming indispensable to jazz. In jazz the alto, tenor, and baritone saxophones are the most common.
Double reed instruments, as the name suggests, use two reeds to produce their stimulus vibration. The two reeds are tightly lashed together. Double reeds generally have the reputation among players as being finicky. The reeds are very easily damaged, although they are not too expensive.
The oboe has a very piercing quality which enables it to be heard through thick textures. Used a great deal in orchestral solos, it can sometimes have a pastoral or thoughtful quality to its tone. It is the soprano member of the double reeds.
The English horn is more or less an alto version of the oboe. The name is misleading because it is neither English nor a true horn (only brass instruments can really lay claim to being "horns"). Its tone is not as bright as that of the oboe and it is not used as often, but it has a very exotic tone and is often used to evoke a feeling of a Middle East setting.
The bassoon is also a double reed, but due to differences in construction, does not sound like a lower version of the oboe. The tenor member of the double reeds, it has a very woody or reedy quality (in one language, its name literally means a bundle of sticks). It tends to be more of an accompanying instrument, but it words well in sustained solos. In faster passages, it sounds rather comical. Composers of cartoon soundtracks make effective use of this trait.
The contrabassoon is a lower version of the bassoon sounding so low that sometimes it sounds as if it doesn't seem to have a pitch. It is an accompanying instrument and is used to reinforce the bass line. It is used (sparingly) as a special musical color.
If you have ever blown across the top of a soda bottle and gotten a tone, you have created an edge tone.
Unlike the other woodwind instruments, when a flute or piccolo produces a musical tone, no part of the instrument is moving. The sound comes exclusively from the stimulus vibration (which is an airstream from the player's lips) and the air column inside the instrument.
The edge tone instruments stimulate their air column by the player blowing across a corner, or an edge. Contrary to what one might expect, when an airstream meets the corner of the instrument's mouthpiece, it doesn't just split into two paths. It will alternate, first going one direction, then the other, back to the first, and so on. This oscillation takes the place of the reed and the double reed in other members of the family, and is powerful enough to move the air inside the instrument.
The flute is the best known edge tone instrument. Many people consider it to be the most beautiful and melodically expressive of the woodwind instruments. It is capable of playing very rapidly and with great agility. An orchestral score will occasionally call for an alto or bass (actually tenor) version of the flute.
The name 'piccolo' literally means "small" in Italian. The piccolo is the smallest and highest pitched of all of the orchestral instruments. Because of its limited range, it isn't a very glamorous solo instrument. However, it is very effective in large ensembles and for special effects. The highest pitched instrument in the orchestra, it cuts through loud and thick textures with great ease.
The wooden ancestor of the flute is called the recorder. A very popular instrument from the Middle Ages up through the 1700s, it was played straight out from the mouth (the flute and piccolo are played in a transverse fashion). Recorders are played today mostly to recreate the sound of Baroque and early music or as teaching tools. In their heyday, the recorder family was a very large one, ranging from bass to sopranino (above soprano).
Because they don't blend very well, there are no regular combinations of woodwinds comparable to a string quartet or a string orchestra. The most common woodwind ensemble is a woodwind quartet, which oddly enough consists of a flute, a clarinet, a bassoon, and a French Horn (which is a brass instrument, not a woodwind). Woodwind instruments are stapes of bands (a marching band, for example).
Except for minor details, the brass instruments share a great deal of similarity in their construction. Because of this, they blend extremely well with each other.
Brasses can play in very soft and rounded tones. They can also play at a deafening volume, which makes them a necessary component in marching bands that need to fill an entire stadium with sound.
Like the woodwinds, the basic structure of all of the brasses consists of a hollow tube. As with the woodwinds, this tube is lengthened or shortened to produce different pitches. Unlike the most of the woodwinds, these tubes are not straight, but curled up many times. Otherwise, you would need a twenty foot space to play some of them. As long as the air column isn't severely constricted, this won't affect the sound.
As with the woodwinds, the only relevant pitch factor is the length, and when the vibrating air column (again, it's still called a column even if it isn't physically straight) is shortened, the pitch rises; when it is lengthened (which is the case in most of these instruments), the pitch drops.
The initial stimulus for the air column comes from the players lips vibrating (or 'buzzing') into a cone shaped mouthpiece. The most important function of the mouthpiece is to give much more control over the buzzing frequency. This basic vibration creates a standing wave in the air column, and the point of all of this, a clear and pleasing musical tone. How hard the player blows affects not the pitch sounded by the instrument, but the amplitude of the air disturbance produced.
Like the woodwind instruments, the brasses change pitch by changing the standing wave inside the instrument, and by changing the length of the air column. Brasses do the latter a little differently from woodwinds. Except for the trombone, which uses a slide to lengthen the instrument, the player will press a valve that will shut off a short section of the air column and open up a longer one. While woodwinds basically work by shortening the air column, brasses lengthen it to produce other notes.
As mentioned above in the section on woodwinds, brass instruments depend more on the mode of changing the standing wave. Before the invention of valves in the 1800s, the trombone was the only one of these instruments that could change its length by use of a slide. The trumpet and French horn could only use the standing wave changes to change pitch rapidly. For slower changes, the player would manually pull a length of tubing from the instrument and replace it with another length, a process that was often noisy.
While these instruments were still used frequently (and some very difficult pieces of music were written for the valveless or "natural" brasses), composers were pretty much at a loss in harmonically complicated passages. Only imaginative writing on the part of the composer and extreme skill on the part of the player saved the day for the brasses.
The first ancestors of the brass family were sheep or ram horns that some caveman blew through and found he could create a pleasing racket. To this day, members of this family are called 'horns' (again, the English horn is a misnomer). One of the most ancient types of instruments, descendants of these prehistoric prototypes are mentioned in the Old Testament of the Bible.
As noted above, the function of the valve is to bypass a small length of tubing, opening up a longer section of the horn, producing a lower note. There are only three valves on most instruments, giving a total of seven possible combinations. Valve 1 lowers the pitch a whole step, valve 2 lowers the pitch 1/2 step, valve 3 lowers the pitch 1 1/2 steps and they are also used in combination to combine the lengthening and lowering effect.
Of the orchestral brass instruments, the trumpet is the most popular and most familiar. It has a clear ringing tone and has a very powerful voice in addition to a softer mellow side. The cornet is similar, but with a slightly less brilliant voice. The difference in tone color comes from slight differences in the shape of the tubing in each of the instruments. In appearance, most people have difficulty telling the difference between the two.
The flugelhorn is a less common member of the family, which is basically an alto (slightly lower) version of the trumpet. Chuck Mangione is the best known player of the flugelhorn.
The french horn is another very common member of the family. Often simply called the 'horn', its pipe is entirely conical and it produces a soft mellow sound that fits in very well with most other instruments. It still can put out quite a bit of volume when necessary. Uncoiled, the average horn contains over 15 feet of tubing, and many horns contain almost twice that much.
The trombone differs from the above instruments in that it has no valves. The air column is lengthened by the use of a slide. Unfortunately (especially for teachers), there are no marks on the slide to guide the player when he extends it. Because of this, listening to a group of beginning trombone players can be profoundly disturbing. Even though it had the pitch changing capability that trumpets and horns lacked, it never was used in a symphony orchestra until the early 1800s, specifically in Beethoven's fifth symphony.
Common trombones are tenor instruments. The tenor trombone contains about 11 feet of tubing. In previous centuries, there was an entire family of trombone ranges, but the only common survivor other than the tenor trombone is the bass trombone.
The tuba has about 24 feet of tubing. It produces a very low, weighty, and usually jocular sound. Rarely played as a solo instrument, like the double bass and the contrabassoon, it is the foundation for its family. A version designed by American composer John Phillip Sousa is called the sousaphone. It contains the same length of tubing, just coiled in a different shape. The sousaphone is a staple of marching bands, where it is not carried by the player as much as it is worn. Fiberglass sousaphones are fairly common, eliminating some of the ever present threat of dents in the brass tubing as well as some of the weight.
The euphonium is essentially a tenor version of the tuba. The baritone horn is similar to a euphonium, but its timbre is closer to that of a trombone.
Often times a score will call for brass players to insert a cone shaped object, called a 'mute' into the bell of the horn. This produces a stopped, tinnier, more forceful sound. Mutes really aren't necessary to make these instruments quieter, as they can easily play very softly.
Groups consisting solely of brass instruments are often called 'brass ensembles' or sometimes called a 'brass choir'.
The fourth traditional orchestral family is the percussion family. While there is by far the greatest diversity in the physical forms of its members, they all produce sound the same way--through all or part of the instrument being struck. This, along with occasionally wildly creative ideas on the part of composers, permits many diverse instruments and objects to be used. Virtually anything that has an interesting sound when struck can be (and probably has been) used. For the sake of special effects, some compositions make use of ball bearings dropped in a water glass and even a burlap bag filled with glass and smashed with a hammer.
Most percussion instruments are a little more tame than these last two examples. The following lists some of the traditional orchestral instruments, even though there are dozens of members. Folk music from around the world makes rich use of percussion instruments that haven't crossed over into mainstream Western music.
Percussion instruments all share certain characteristics of their sound. None of these instruments is capable of sustaining a sound. As soon as the instrument is struck, the sound begins to die away. Some, such as the gong or the piano die away slowly, but nevertheless, none of them can sustain a sound in the full sense of the word (keep sounding at a steady volume level).
Generally they will all have a very sharp attack (the time for the sound to rise from silence to its loudest point), and usually, a quick decay. Many percussion instruments, such as the drums and cymbals, produce white noise, which is an unordered mixture of many unrelated frequencies.
There are a number of ways to classify the members of this diverse family, but each one has its own drawbacks.
One that's as good as any is to group it into four classes--(1) pitched percussion, (2) non-pitched wood, (3) non-pitched metal, and (4) non-pitched membranous. One could easily add a fifth--everything else not covered in the above. A lot of exotic effects would certainly fall here.
PITCHED PERCUSSION
All instruments that are able to sound at a definite pitch (in other words, be tuned to a particular note) fall into this category, regardless of their construction. Members you are likely to be familiar with include the chimes (also known as the tubular bells), the glockenspiel (sometimes called orchestral bells), other types of bells, the vibraphone, xylophone, marimba, and the kettledrum (sometimes called the timpani).
The celesta is played with a keyboard similar to that of a piano. It contains little metal bars that are struck, sounding a bit like small chimes.
More exotic members include the flexotone, a little metal plate with mallets that hit it, producing a weird almost whistling sound.
Perhaps the most notable pitched percussion instrument is one not usually thought of as a member of the percussion family--the piano. The internal mechanism, perfected by Bartolommeo Cristofori in the early 1700s, strikes the strings with felt-tipped hammers.
When heard with other percussion instruments, it sounds very much in context with its sharp attack and tone that dies away (slowly, but it does die away).
NONPITCHED METAL
A number of orchestral instruments produce sounds without a definite pitch. Examples of these made of metal include the cymbals, the gong (which has an especially long decay in its sound), and the triangle. Triangles are sometimes made to have a pitch, but most of the time they will produce a high non-pitched clang.
When people see an orchestral concert where one musician's sole job seems to be playing the triangle, a usual question is "Is that all he does for a living?"
The answer is no--musicians will be percussion specialists, being competent on many different instruments. That particular piece of music called for a triangle, and well, someone had to do it. . .
Many percussionists are also expert pianists, vibraphonists, or specialize in other instruments of the family a bit more challenging than the triangle.
NONPITCHED WOOD
Instruments without a definite pitch and that are made of wood include woodblocks, claves, castanets, the guiro, and maracas.
Many of these instruments are commonly found in Latin American music. Quite a large number of somewhat folk instruments will be made of wood.
NONPITCHED MEMBRANOUS
A membrane is some kind of thin "skin" stretched over a chamber or hollow space of some sort. Early instruments made use of animal skins. Today, many of the instruments use plastic in place of the skin.
The most common members and the drum family. These include the snare drum, bass drum, tenor drum, the tom-toms, but not the timpani--because it is tuned to a definite pitch.
Others include the tambourine, and the occasionally used whip. When used in an orchestra, the whip is simply two pieces of leather cracked together, unlike a bullwhip that you might see in a Western or a rodeo.
With the exception of the piano, percussion instruments have been kept in the background for centuries. In the 20th century, composers began looking for new sounds, new tone colors and eventually turned to the percussion family for their resources. A movement called "primitivism", brought on in part by Igor Stravinsky, began incorporating them much more heavily into the musical mainstream.
Primitive societies, not having the technical or mechanical aptitude to create something on the order of a Stradivarius violin or a French horn, have concentrated on the musical strengths available to them--music that heavily emphasizes rhythm.
Discoveries of these primitive cultures by anthropologists have inspired many artists and creators. Stravinsky, mentioned above, and Pablo Picasso are among the creative artists who found this "new" resource to be a fresh and exciting source of creative inspiration.