Atransposing instrument is amusical instrument for which music notation is not written atconcert pitch (concert pitch is the pitch on a non-transposing instrument such as the piano). For example, playing a writtenmiddle C on a transposing instrument produces a pitch other than middle C; that sounding pitch identifies theinterval of transposition when describing the instrument. Playing a written C onclarinet orsoprano saxophone produces a concert B♭ (i.e. B♭ at concert pitch), so these are referred to as B♭ instruments. Providingtransposed music for these instruments is a convention ofmusical notation. The instruments do not transpose the music; rather, their music is written at a transposed pitch. Where chords are indicated forimprovisation they are also written in the appropriate transposed form.
For some instruments, a written C sounds as a C but is in a differentoctave; these instruments are said to transpose "at the octave". Pitches on thedouble bass sound an octave lower than written, while those on thepiccolo andcelesta sound an octave higher, and those on theglockenspiel sound two octaves higher.
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Some instruments are constructed in a variety of sizes, with the larger versions having a lowerrange than the smaller ones. Common examples areclarinets (the high E♭ clarinet, soprano instruments in C, B♭ and A, the alto in E♭, and the bass in B♭),flutes (thepiccolo, transposing at the octave, the standard concert-pitch flute, and thealto flute in G),saxophones (in several octaves in B♭ and E♭), andtrumpets (the common instrument in B♭, instruments in C, D and E♭, and thepiccolo trumpet transposing at the octave). Music is often written in transposed form for these groups of instruments so that thefingerings correspond to the same written notes for any instrument in the family, even though the sounding pitches will differ. A musician who plays several instruments in a family can thus read music in the same way regardless of which particular instrument is being used.
Instruments that transpose this way are often said to be in a certain "key" (e.g., the "B♭ clarinet" or "clarinet in B♭"). This refers to the concert pitch that is heard when a written C is played on the instrument in question. Playing a written C produces a concert B♭ on a B♭ clarinet, a concert A on an A clarinet, and a concert C on a C clarinet (this last example is a non-transposing instrument).
Beforevalves were invented in the 19th century,horns andtrumpets could play only the notes of theovertone series from a singlefundamental pitch. (Exceptions includedslide-bearing versions such as thesackbut and finger-hole horns like thecornett andserpent.) Beginning in the early 18th century, a system ofcrooks was devised in Germany, enabling this fundamental to be changed by inserting one of a set of crooks between the mouthpiece and the lead pipe of the instrument, increasing the total length of its sounding tube. As a result, all horn music was written as if for a fundamental pitch of C, but the crooks could make a single instrument a transposing instrument into almost any key.[1]
Changing these lead-pipe crooks was time-consuming, and even keeping them from falling out while playing was a matter of some concern to the player, so changing crooks could take place only during substantial rests. Medial crooks, inserted in the central portion of the instrument, were an improvement devised in the middle of the 18th century, and they could also be made to function as a slide for tuning, or to change the pitch of the fundamental by a semitone or tone. The introduction of valves made this process unnecessary, though many players and composers found the tone quality of valved instruments inferior (Richard Wagner sometimes wrote horn parts for both natural and valved horns together in the same piece). F transposition became standard in the early 19th century, with the horn sounding a perfect fifth below written pitch in treble clef. In bass clef, composers differed in whether they expected the instruments to transpose down a fifth or up a fourth.[2]
In Germany during the Baroque period, instruments used for different purposes were often tuned to different pitch standards, calledChorton ("choir pitch") andKammerton ("chamber [music] pitch"). When playing together in an ensemble, the music of some instruments would therefore be transposed to compensate. In many ofBach's cantatas, the organ part is notated a full step lower than the other instruments.[3] Seepitch inflation.
Some present day early-music ensembles combine instruments tuned to A415 with instruments tuned toA440. Since these pitches are approximately asemitone apart, the music for one set of instruments may be transposed to match the pitch of the others. Modern builders ofcontinuo instruments sometimes includemoveable keyboards which can play with either pitch standard.[4] Some harpsichords are made with a mechanism that shifts the keyboard action right or left, causing each key to play the adjacent string. If A4 is tuned at A415, that key can then play either the A♯ at 440 Hz or the A♭ at 392 Hz. The top or bottom key on the instrument will not produce sound unless the builder has added extra strings to accommodate this transposition.
Some instruments have ranges that do not fit on the staff well when using one of the common clefs. In order to avoid the use of excessiveledger lines, music for these instruments may be written one, or even two,octaves away from concert pitch, using treble or bass clef. These instruments are said to "transpose at the octave"—their music is not written in a differentkey from concert pitch instruments, but sound one or two octaves higher or lower than written.
Double bass,bass guitar,guitar, andcontrabassoon sound an octave lower than written.Piccolo,xylophone,celesta, and somerecorders (sopranino,soprano,bass and sometimesalto) sound an octave above the written note.Glockenspiel,garklein recorder, andcrotales sound two octaves above the written note.
Most authorities include this type of notation in the definition of "transposing instruments",[5] although it is a special case in the sense that these instruments remain in the same key as non-transposing instruments.
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Manywoodwind instruments have one major scale whose execution involves lifting the fingers more or less sequentially from bottom to top. Onflute andsaxophone, and in the second register of theclarinet, this scale is notated as a C scale. This is not the case foroboe (where this scale is D) orbassoon (where it is F). The note written as C sounds as the note of the instrument's transposition: on an E♭ alto saxophone, that note sounds as a concert E♭, while on an A clarinet, that note sounds as a concert A.
Brass instruments, when played with no valves engaged (or, fortrombones, with the slide all the way in), play a series of notes that form the overtone series based on some fundamental pitch, e.g., the B♭trumpet, when played with no valves engaged, can play the overtones based on B♭. Usually, that pitch is the note that indicates the transposition of the instrument. Trombones are an exception: while tenor and bass trombones are pitched in B♭, and the alto trombone is in E♭, they read at concert pitch. This convention is not followed in British Brass Band music, where tenor trombone is treated as a transposing instrument in B♭.French horn is treated as a transposing instrument in F even though many horns have two (or even three) different sets of tubing in different keys (the common double horn has tubing in F and B♭).
In general, for these instruments there is some reason to consider a certain pitch the "home" note of an instrument, and that pitch is usually written as C for that instrument. The concert pitch of that note is what determines how we refer to the transposition of that instrument.
Infull scores, music for transposing instruments is generally written in transposed form, just as in the players' parts. Since the beginning of the 20th century, some composers have written orchestral scores entirely in concert pitch, e.g. the score ofSergei Prokofiev'sPiano Concerto No. 1 in D♭.
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