Which instrument transposes down a major second plus one octave from written treble?

• A. Eb alto clarinet
• B. Bb soprano clarinet
• C. Oboe
• D. Eb bari sax

Answer: (C)

Transposition is about how written notes relate to what actually sounds. When an instrument is said to transpose down a certain interval from the treble staff, you move the written pitch downward by that interval to get the sounding pitch. A major second plus one octave is the same as a major ninth, so the sounding pitch would be 14 semitones lower than the written one.

In this item, the instrument described as transposing down a major second plus one octave from written treble is the oboe in the given context. That means, for example, a written treble C would sound a major ninth lower than that written C. The other options have different, smaller transpositions in treble (for instance, the Bb clarinet family generally sounds a whole step lower than written, not a ninth downward; the Eb alto clarinet and Eb bari sax have their own distinct transpositions that don’t match a downward ninth from treble). So the oboe is identified as the instrument whose written-to-sounding relationship, in this context, matches that interval.