Posted by John Swensen on August 23, 2000 at 14:42:43:
In Reply to: Transposition Aids posted by Dan Schultz on August 23, 2000 at 14:16:04:
Dan,
A transposing instrument, say a Bb clarinet, sounds a concert Bb when it plays a written C. To play a C flute part on a Bb clarinet, you need to play a whole tone higher on the clarinet than is written (that is, see a C, play the clarinet's D). To play a Bb clarinet part on a C flute, play a whole tone lower (see a C, play the flute's Bb).
To transpose from one transposing part to another you need to do a little more math. For example, to play an F horn part on a Bb trumpet, note that the horn sounds a fourth above (or a fifth below) its written part, and the trumpet sounds a whole tone below its written part, so you need to play the notes a fifth above (or a fourth below) the horn part on trumpet to sound the same pitch (see a C, want to sound an F, play the trumpet's G).
Normally you add flats or sharps to the key signature to simplify the reading; these correspond to the key signature of the note played to match the written note. For a flute part on a Bb clarinet, you need to play a D to sound a C, so add two sharps to the key signature (or subtract two flats). For a clarinet part on a flute, you need to play a Bb, so add two flats (or subtract two sharps). For a horn part on a Bb trumpet, you play a G, so add one sharp.
For tonal music, it may help to start by playing a major scale in the transposed key signature, then a major arpeggio, then start playing. It can be frustrating, at first, but all advanced trumpet and horn players learn to transpose while sight-reading, often assuming one arbitrary keyed instrument playing a part transposed for another arbitrary keyed instrument (as in, "play this part in H (B natural), assuming you have a Gb trumpet").