FA-80883 / Music interval and transposition theory / Member archive

Key-aware MIDI note spelling: B sharp keeps the sounding octave number · case 03

In C# major, middle C is spelled B#4, an octave above the sounding pitch, instead of B#3.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input [midi, fifths] with midi 0..127 and fifths -7..7. Use flat names when fifths < 0, sharp names otherwise; in keys with at least six sharps pitch class 5 is E#, with seven sharps pitch class 0 is B# of the previous octave, and with at least six flats pitch class 11 is Cb of the next octave. Octave -1 starts at key 0. Invalid input returns None.

Why this case matters

Pitch spelling and interval arithmetic decide the notes that notation, transposition and analysis tools display or play.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
oracle 4	`"B#4"`	`"B#3"`	Failed

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