transposing instrument

transposing instrument a musical instrument whose part in a score is written at a different pitch than that actually sounded. Such an instrument is usually referred to by the keynote of its natural scale—the clarinet in A, for example—in which case A is sounded when the tone C appears in the musical notation. Since A is a minor third below C, the part for this instrument must be written a minor third higher than it is to sound. Transposing instruments were necessary in the 17th and 18th cent. when the natural brasses and the clarinets could be played easily in only a few keys; they were therefore built in specific keys. Although improved construction in the 19th cent. obviated this necessity, all clarinets , the English horn , oboe , French horn , trumpet , alto flute , cornet , and most saxophones are transposing instruments. Parts for the piccolo, double bass, and contrabassoon are written an octave below or above actual pitch to avoid ledger lines, but this is not, strictly speaking, transposition.

transposing instruments. Instruments which are not notated at their true pitch but (mechanically and without any effort on the player's part) produce the effect of that pitch. For example, the cl. is made in several sizes, the B♭ and A being the most often used because these keys reduce the difficulty of playing in the flat and sharp keys, respectively, by reducing the number of flats or sharps with which the player has to cope. In the B♭ instr., that key is to its player the ‘natural key’ (as C is to the pianist): the player faced with music in (say) the key of E♭ finds the music written in the key of F, i.e. there are 2 flats fewer to consider. Similarly with the A instrument a piece written in the key of B is notated in the key of D, i.e. there are 3 sharps fewer to consider. Thus music for the B♭ cl. is notated a tone higher than it is to sound and music for the A cl. a minor 3rd higher. Many players, with improved mechanism and developed technique, use the B♭ instrument for all keys, making the transposition mentally. On the rare C cl. the note sounded is the note written; the E♭ cl. transposes tones higher than written note; the bass clarinet in B♭ an octave and a tone lower.

 The transposing instruments are as follows: (a) bass fl.; (b) cor anglais, ob. d'amore, ob. in E♭, heckelphone, sarrusophone; (c) cl. in B♭ and A, bass cl., high cl. in E♭ and D, alto cl. in E♭ and F, basset hn., pedal cl.; (d) saxophones; (e) cornets; (f) French hns.; (g) tpts.; (h) saxhorns; (i) kettledrums (up to Mozart's period, but excluding Handel).