Transposing Instrument - Mechanical and Physical Considerations

Mechanical and Physical Considerations

Woodwind instruments each have one major scale whose execution involves lifting the fingers more or less sequentially from the bottom to top. This scale is usually the one notated as a C scale (from C to C, with no sharps or flats) for that instrument. 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♭, on an A clarinet, that note sounds as a concert A. The bassoon is an exception; it is not a transposing instrument, yet its "home" scale is F. For tin whistles the "home" scale is notated as D major rather than C major — the most common whistle, pitched in D, is therefore not a transposing instrument.

Brass instruments, when played with no valves engaged (or, for trombones, 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 that brass instrument. Trombones are an exception — they read at concert pitch, although tenor and bass trombones are pitched in B♭, alto trombone in E♭. Music for baritone or euphonium is sometimes written in treble clef, transposed to B♭, but sometimes in bass clef at concert pitch.

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.