FA-81270 / Music interval and transposition theory / Member archive

Diatonic step transposition within a major key: no octave carry past the seventh degree · case 05

B4 up one step in C major gives C4 instead of C5: the result wraps within the original octave.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input [tonic, notes, steps] where tonic is a MIDI reference note. Each note must belong to the major scale on the tonic (else return None). Its scale position is its degree plus 7 per octave counted from the tonic note with floor division (notes below the tonic note are in negative octaves). Move by the signed number of steps and return the resulting MIDI notes.

Why this case matters

Harmonisers and sequence generators transpose melodies diatonically rather than chromatically.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
oracle 0	`[60]`	`[72]`	Failed

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