FA-80844 / Music interval and transposition theory / Member archive

Spelled pitch to MIDI key number: octave numbered from zero at middle C minus four · case 04

Every spelled pitch lands exactly one octave low, so C4 reports 48 and A4 reports 57.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input a spelled pitch string: uppercase letter A-G, any run of accidentals (# = +1, b = -1, x = +2), then a signed integer octave where C4 = 60 and C-1 = 0. Return the MIDI key number, or None for malformed text or results outside 0..127.

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 0	`null`	`0`	Failed

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