Which instrument sounds as written when notated in bass clef but sounds a major ninth lower when read in treble clef?

• A. Euphonium
• B. Tuba
• C. Bassoon
• D. Baritone horn

Answer: (A)

Think about how written notes map to sounding pitches for instruments that are transposing and use different clefs. The euphonium is a Bb instrument whose parts are typically written in bass clef so the range sits comfortably and the sounding pitch is notated directly. If you took the same notes and read them in treble clef, the pitches you’d hear would be lowered by an octave plus a whole step, which is a major ninth. That combination—bass-clef notation sounding as written, but treble-clef reading producing a major ninth lower—fits the euphonium.

The other choices don’t fit this exact clef-and-transposition relationship as naturally.