The Perception of Timbre
In Unit 1, we learned that there are four basic characteristics of sound: pitch, duration, volume, and timbre. When we hear the exact same pitch played for the same duration at the same volume on two different instruments, the only difference is TIMBRE (also called TONE COLOR). We generally attribute differences in timbre to differences in sound sources, and often label timbres by the sources that produce them. Thus, we might speak of a “trumpet timbre” or “acoustic guitar timbre,” for example. We also use a variety of adjectives to describe various timbres, such as bright, dark, nasal, rounded, and so on.
The Agents of Timbre
There are several factors that contribute to our perception of timbre. These include the relative intensities of the various overtones present in any sound, how those overtones evolve over the duration of a note, and additional aspects of how sounds are produced.
The Relative Intensities of Overtones
As we learned in Unit 3, just about every pitch we hear is actually a combination of the fundamental (the pitch we perceive as the pitch) and a series of overtones which vibrate at frequencies in whole-number multiples of the fundamental’s frequency (1x, 2x, 3x, 4x, etc.). We don’t perceive all these overtones as separate pitches (like the pitches in a chord). Instead, we perceive the pitch of only the fundamental, and perceive the combination of overtones as timbre.
When we hear an instrument with a rich timbre play the pitch A2, (like a tuba, cello, or piano, for instance), in that pitch we also hear traces of A3, E4, A4, C-sharp5, E5, etc. But, instead of hearing all those trace waves as different and distinct pitches, we hear them as components of the timber of that lower note. Changing the strength of these various subservient overtones changes the timbre. (But, increasing them dramatically would, in fact, make us hear complete distinct pitches!)
For an aural/visual demonstration, check out this youtube video that shows the strength of different overtones for many different instruments playing the same pitch.
Attack, Decay, Sustain, Release
The relative intensities of overtones in a pitch don’t remain constant from the beginning of a note through its end.1 Instead, the various overtones change in intensity over the time any single note is sounding. Just about every musical sound, even a very short one, will differ in timbre among its ATTACK (the very beginning of the note), its DECAY (the decrease in sound immediately after its attack), its SUSTAIN (the sound while a note is being held for a while), and its RELEASE (the very end of the note). It turns out that our ears learn to recognize the characteristic timbres of all these phases for various instruments and voices. In fact, timbres change constantly, even during each of these phases, and we learn to hear that as part of timbre, too. (We refer to this timbral change over time SPECTRAL EVOLUTION)
Other Factors that Contribute to Timbre
There are other factors that also contribute to our perception of timbre. These include the changes in character between low and higher registers on a single instrument or voice. For example, the timbre of a clarinet is quite dark and rich in its low register, but much more bright and intense (and some would say even shrill) in its highest register. Nonetheless, we recognize these differences as part of a distinctive “clarinet timbre.” There are also some instrument-specific idiosyncrasies that play a hand in what we perceive as timbre, especially peculiarities of attack, such as the rosin-laden horsehair of a violin bow starting a string’s vibration, the spit in a trombone player’s mouthpiece, the slight “quack” of an oboe player’s reed, the squeak of a guitar player’s fingers along the strings, and so on.
Generic Classification of Musical Instruments
Some musicians use very broad categorizations for instruments based on the way those instruments produce sounds. The four main categories under this system are idiophones, membranophones, chordophones, and aerophones.
An IDIOPHONE is an instrument that produces sound through the vibrations of the entire instrument itself. In other words, the main body of the instrument vibrates, not an attached string, membrane, or body of air. Many idiophones are struck (like the wood block or triangle), but others are scraped (guiro), shaken (maracas), plucked (like the kalimba [thumb piano] or music box), or even caused to vibrate through friction (like the musical saw and glass harmonica).
A MEMBRANOPHONE is an instrument that produces sound through the vibration of a membrane. Membranophones are constructed by stretching a membrane (often a skin or plastic sheet) over some kind of frame. Most membranophones are caused to vibrate by being struck (with the hand or a beater), but some are rubbed, and a few use a string attached to the membrane which induces vibrations when pulled taught and stroked. Drums (such as the bass drum, the talking drum, and the tympani) are membranophones. Even the kazoo is a membranophones: its membrane is caused to vibrate sympathetically with the player’s voice.
A CHORDOPHONE is an instrument that produces sound through the vibration of a string. The strings of some chordophones are plucked (like the guitar and harp), others are bowed (like the violin) although many bowed instruments may also be plucked, and some are struck (like the piano and hammered dulcimer). Aerophones An AEROPHONE is an instrument that produces sound through the vibration of a body of air. Most aerophones contain a vibrating body of air inside them (such as the flute, tuba, and pipe organ).
Some musicians admit yet another category: electrophones. An ELECTROPHONE is an instrument (such as a synthesizer) that produces sound generated by electricity that moves a speaker to produce vibrations. Because electrophones can produce any timbre imaginable, for the purposes of studying timbre this category is not very useful.
Western European Art-Music’s Classification of Musical Instruments
For hundreds of years, Western musicians have classified instruments into the following families: strings, woodwinds, brass instruments, and percussion. These classifications have served well, particularly when thinking about the instruments in the Western classical orchestra.
The Western string family consists of four types of chordophones: the violin, viola, cello, and double bass. All are four-stringed instruments with resonating bodies made of wood. Musicians produce sound on string instruments mainly by passing a horse-hair bow across each string, causing it to vibrate. The VIOLIN plays mostly in the treble-clef register. It can soar rather high (well above the staff). In the Western classical orchestra, a section of violins most often plays the main melodic line. Here is a link to a violin performance: http://www.youtube.com/watch?v=L05xsjRvFEw The VIOLA plays in a register between the treble and bass clefs. (In fact, the viola usually reads in the alto clef, whose register is right in between the treble and bass clefs.) The timbre of the viola is similar to that of the violin, but is somewhat darker and richer, due to the larger size of its resonating body. Violas often play inner parts, but they do take more prominent roles from time to time. Here is a link to a viola performance:
The CELLO plays mostly in the bass-clef register. It can also play much higher, particularly in some solo literature (in which case it may even be written for a time in the treble clef). Cellos often play bass lines as well as taking on some melodic passages. The timbre of the cello is even darker and fuller than that of the violin and viola, due to the even larger size of its resonating body. Because of its size, cellists must sit down to play. Here is a link to a classical cello performance:
The DOUBLE BASS (also called the CONTRABASS, STRING BASS, UPRIGHT BASS, or simply BASS) plays in the bass-clef register, even lower than the cello. The timbre of the double bass is much deeper than the other three string instruments, due to the even larger size of its resonating body, but is also more nasal in character, due to the different shape of its body (especially the sloped shoulders). Double basses usually play bass lines. In jazz, the double bass is often plucked (pizzicato) rather than bowed. Because of its particularly large size, double-bass players must stand and hold the instrument on the floor to play. Here is a link to a double bass performance:
And here’s another, playing jazz:
The Western woodwind family consists of four basic types of aerophones: the flute, oboe, clarinet, and bassoon. In addition, the various saxophones are members of the woodwind family. All produce sounds through a vibrating body of air inside a metal or wooden tube. The FLUTE plays mostly in the treble-clef register. It has a relatively “pure” timbre (rather close to a pure sine wave). Flutes are essentially narrow cylinders with holes for altering the length of the body of air inside. Flutes are usually made of metal nowadays, although they were often made of wood in earlier times. Musicians produce sounds on the flute by blowing across an open hole on the side near the of the flute, which causes the body of air in the flute to vibrate (much like the way you can make a sound by blowing across the open top of a soda bottle). Here is a link to a flute performance:
The OBOE also plays mostly in the treble-clef register. It has a much more nasal timbre than the flute. Musicians produce sounds on the oboe by blowing a double reed, the two parts of which vibrate, producing a sound and causing the body of air in the oboe to vibrate as well. Oboes are made mostly of wood. Here is a link to an oboe performance:
The CLARINET also plays mostly in the treble-clef register, although it can go nearly an octave lower than the flute and oboe. It has a more pungent timbre than the flute, but is somewhat softer or rounder than the oboe. Musicians produce sounds on the clarinet by blowing a single reed, which vibrates, producing a sound and causing the body of air in the clarinet to vibrate as well. Clarinets are made mostly of wood. Here is a link to a clarinet performance:
The BASSOON plays mostly in the bass-clef register, although it can play rather high (in the treble-clef range) at times. Like the oboe, it has a somewhat nasal timbre, but its lower register softens this somewhat. Some musicians remark that the bassoon’s timbre is close to that of the human voice. Musicians produce sounds on the bassoon by blowing a double reed, which vibrates, producing a sound and causing the body of air in the bassoon to vibrate as well. Bassoons are made mostly of wood. Here is a link to a bassoon performance:
The SAXOPHONE family consists of many instruments (alto sax, tenor sax, etc.) which play in a wide variety of registers. Saxophones are closely related to clarinets, but because they are made of metal (not wood like the clarinet), they have a brighter or richer timbre. Musicians produce sounds on saxophones by blowing a single reed, which vibrates, producing a sound and causing the body of air in the saxophone to vibrate as well. Saxophones are made of metal. Here is a link to an alto saxophone performance:
And here is a link to a baritone saxophone performance:
The Western brass family also has four commonly-used members (all aerophones as well): the trumpet, French horn, trombone, and tuba. Brass players produce sounds by buzzing their lips into a cup-shaped mouthpiece, which sets in motion a vibrating body of air inside a metal tube. All brass instruments are made of metal (often brass, but other metals are used as well). The TRUMPET plays mostly in the treble-clef register. The trumpet produces a bright sound, especially in its higher registers. Trumpet players produce various pitches through two different means: tightening their lips (which will produce different notes in the overtone series), and depressing VALVES (which will increase the overall length of the tubing in which the air vibrates, thereby creating a new fundamental and potential overtones). Here is a link to a trumpet performance:
The TROMBONE plays mostly in the bass-clef register, although it can play rather high at times (well up into the treble-clef range). The trombone can produce a deeper, larger sound than trumpets and French horns do. Trombonists use the same lip-tightening technique other brass players do, but they increase the length of the instrument’s tubing through means of a SLIDE.
Here is a link to a trombone performance:
The TUBA plays in the bass-clef register. As the largest of the brass instruments, it produces a deep, massive sound. Like trumpeters and French horn players, tubists use a combination of lip-tightening and valves to produce different pitches. Here is a link to a tuba performance:
Percussion instruments generally produce sound by being struck, scraped, or shaken (hence the name “percussion”). One popular way to classify percussion instruments separates them into two broad categories: definite pitch and indefinite pitch. Instruments of definite pitch (like a xylophone or tympani) produce pitches that are capable of being identified, matched, and used in melodies or harmonies. Instruments of indefinite pitch (like a cymbal or castanets) produce no discernable pitch. Most percussion instruments are idiophones or membranophones, but there are some percussion chordophones and aerophones, too.
There are numerous percussion instruments throughout the world, and the Western orchestra has incorporated various kinds. We’ll examine a few that have appeared in Western orchestras over the years.
TYMPANI (membranophones colloquially called kettledrums) are the earliest percussion instruments to make a permanent home in the Western orchestra. Tympani are constructed of membrane (or “head”) stretched across a large metal bowl. Players strike the membrane with a stick or mallet to produce a sound. Tympani produce definite pitch, and can be tuned by tightening or loosening the membrane. Here is a link to a tympani performance:
Among the many other membranophones that have appeared in the Western orchestra, we’ll examine one more: the BASS DRUM. The bass drum also plays a central role in the drum kit found in many rock bands and jazz ensembles. The bass drum is a membranophone of indefinite pitch, constructed of two membranes stretched across the two parallel open ends of a short cylinder.
Players produce sound by striking the bass drum with a mallet or beater. Other drums used frequently in the orchestra include the snare drum and tom-tom. Here is a link to a bass drum demonstration:
CYMBALS are indefinite-pitch idiophones made of thin, round plates of metal. Cymbals may be suspended on a stand and struck by a stick or mallet, or held in pairs and crashed together (hence the term “crash cymbal”). Other large, round, metal percussion instruments include the tam-tam and various gongs. Here is a link to demonstrations of both crash cymbals and suspended cymbals (the suspended cymbal demonstration begins at 4:40):
Keyboard percussion instruments derive their name from their construction, consisting of bars laid out in the same manner used in keyboard instruments like the piano (see the figures towards the end of Unit 5 for examples of this layout). Among the many keyboard percussion instruments used in the orchestra, we’ll look at one: the XYLOPHONE, which is constructed of wood bars struck by mallets. Each wooden bar is an idiophone that produces a unique definite pitch. Other keyboard percussion instruments include the marimba and vibraphone. Here is a link to a xylophone performance:
There are many more percussion instruments used in the Western orchestra — such as the triangle, glockenspiel, wood blocks, and maracas — and even more are used in various kinds of musics around the world, but we’ll keep things simple and stop after having examined these few.
One of the special things about keyboard instruments is that they physically and visually represent a continuous range of Western pitches in their very construction. (Consult the end of Unit 5 for images of this.) When you look at a musical keyboard, you see the structure of the staff in the white keys, the intervals of the C-major scale in the whole and half steps between the white keys, the notes that require sharps and flats in the black keys, and so on. The PIANO is arguably the most ubiquitous keyboard instrument in the world. When a player presses a piano key, the key moves a hammer that strikes a string (or group of strings tuned alike) that vibrates, producing a pitch. In this way, the piano is both a percussion instrument (because of the hammer strike) and a string instrument. Most modern pianos have 88 keys that span pitches from A0 to C8. The piano produces a distinctive timbre, growing from richly dark in the lower register to exceptionally bright at the top. The name piano derives from pianoforte (which literally means quiet-loud), so named because it was the first keyboard instrument capable of producing a wide range of dynamics in response to a player’s touch on the keyboard. Here is a link to a piano performance:
The ORGAN is among the world’s largest instrument. Organs produce sound when air is blown through a pipe (usually made of metal or wood) and caused to vibrate. Players select pitches through keyboards — usually several for the hands (called manuals) and one for the feet (consisting of pedals laid out like a keyboard, called a pedalboard). Organs typically have hundreds of pipes, organized into ranks of similar timbres, which can be selected by the player pulling out various stops (hence the phrase to pull out all the stops for bringing everything to bear). In general, the organ’s timbre (and overall presence) is quite powerful, sometimes even overwhelming. For this reason, organs found a home in Western churches, ballparks, skating rinks, and other large venues. Here is a link to an organ performance (be sure to see the shot of the pipes at 0:28 and observe the pedal work beginning at 1:43):
The HARPSICHORD was popular in Western European Art music during the Renaissance era (roughly 1400–1600 CE) and especially during the Baroque era (roughly 1600– 1750 CE). Harpsichords have one or more keyboards, with each key connected to a plectrum that plucks a string. The timbre of the harpsichord is rather thin and somewhat delicate, although larger ones have multiple choirs of strings that can be sounded simultaneously to produce louder sounds. Some describe the harpsichord as “nasal” or even “tinny” at times. Harpsichords typically span four or five octaves (compared to the more than seven spanned by the piano). Here is a link to a harpsichord performance:
SYNTHESIZERS usually use keyboards as controllers, too, but for the purposes of learning about timbre this distinction is useless. Synthesizers are capable of mimicking the sounds of many instruments as well as producing new sounds you’ve never heard before, and are therefore beyond the scope of this unit.
Western European Art Music’s Classification of Musical Voices
Western musicians have also classified voices into various categories. Obviously, the broadest distinction can be made between female and male voices. We can usually (although not always!) distinguish between male and female voices rather quickly just by listening. Beyond that, there are categories of voices, which are based on range and which are usually associated with distinct timbres
There are two basic kinds of high voices. A SOPRANO is the highest human voice. Sopranos generally sing between C4 (middle C) and C6 (although not all sopranos prefer to sing C6 very often!). Soprano voices have rather bright timbres. Here is a link to a soprano performance:
An ALTO sings lower than a soprano, generally between G3 and G5. Alto voices are generally darker in timbre than sopranos. Here is a link to an alto performance (this cracks me up!):
There are also finer distinctions among female voices. These include MEZZOSOPRANOS, who sing slightly lower than sopranos, and CONTRALTOS, who sing slightly lower than altos.
There are two basic kinds of low voices. A TENOR is the usually the higher of the two. Tenors generally sing between C3 and A4 or C5. Tenor voices have rather bright timbres. Here is a link to a tenor performance (the tenor enters at 0:44):
A BASS sings lower than a tenor, generally between F2 and E4. Bass voices are generally darker in timbre than tenors. Here is a link to a bass performance:
There are also finer distinctions among male voices. These include COUNTERTENORS, who sing in the same range as altos, BARITONES, who sing slightly higher than basses, and BASSO PROFUNDOS, who sing even lower than basses.
The GUITAR has become a fixture in Western music over the past century. Both acoustic and electric guitars are found in much rock, folk, and jazz music. Lead guitarists (often playing soaring melodies) and rhythm guitarists (playing chords) form a central part of many groups. Guitarists strum or pluck the strings of the guitar, which then vibrate. Guitarists produce different pitches through choosing from among variously-tuned strings, and through shortening the vibrating length of the strings by pressing them against the fretboard with the other hand. Here is a link to an acoustic-guitar performance:
And here is a link to an electric-guitar performance: