How can you tell if an instrument is no-transposing or transposing e.g. trombone?

Question

How can you tell if an instrument is no-transposing or transposing e.g. trombone?

Answer 1

There are several ways.

1.  If it's a bass clef instrument, then it's a non-transposing instrument.  All bass clef instruments are non-transposing.  (Thus, trombone is a non-transposing instrument.)  The double bass and the tuba are exceptions (sort of) in that they sound an octave below the written note (although technically the right note name comes out.)

2.  Look at a part written for the instrument.  Most of the time it will say on the part whether the instrument is transposing or not.  (a "B Flat Clarinet," for example, is a transposing instrument.  Whereas, a "C FLUTE" is not.)

3.  Play that instrument's C and compare it to the C on the piano.  If they sound alike, then the instrument is non-transposing.  If it's different, figure out what note on the piano corresponds to that instrument's C.  That's the name of the instrument.

Answer 2

If you are told to play a "concert B flat pitch" and that means you have to play a B flat, you are playing a non-transpositional instrument. If you have to play some other note, you are playing a transpositional instrument.