FA-81118 / Music interval and transposition theory / Member archive

Transposing instrument written and concert pitch: written part transposed toward concert pitch · case 03

A concert C for Bb clarinet is written as Bb instead of D: the written part moves the same way as the sounding pitch.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input [instrument, pitch, direction]. Each instrument has a stipulated sounding offset in semitones (concert = written + offset): Bb clarinet -2, A clarinet -3, F horn -7, Eb alto sax -9, Bb tenor sax -14, Eb baritone sax -21, guitar -12, piccolo +12, D trumpet +2, flute 0. direction to_concert adds the offset, to_written subtracts it. pitch and result must be MIDI 0..127; otherwise, or for unknown instrument or direction, return None.

Why this case matters

Score and part generators convert between written and sounding pitch for every transposing instrument.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
oracle 0	`51`	`69`	Failed

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