Bb

In this section

• What does 'sounds a major ninth lower' mean

  A major ninth is an octave plus a whole step. On a treble-clef euphonium part, a written C sounds the B♭ a major ninth below — the fixed interval that defines the brass-band transposition.

• Can a trumpet or cornet player read a euphonium part

  A treble-clef brass band euphonium part reads exactly like a B♭ trumpet part — same clef, same transposition — just an octave lower in sound. A cornet player can sight-read it immediately.

• Why is my brass band euphonium part written in treble clef?

  British brass bands notate almost every instrument in transposed treble clef so players can switch horns without relearning to read. Your B♭ euphonium sounds a major ninth below the written note.