FA-81148 / Music interval and transposition theory / Member archive

Written key signature for a transposing part: flat keys folded into sharp side · case 03

An F major part with no shift is written with eleven sharps instead of one flat.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input [concert_fifths, written_semitones_above_concert] with concert_fifths -7..7 and an integer semitone shift. The key moves by (7 * shift) mod 12 fifths; the written signature is concert_fifths plus that move, then normalised into -5..6 by adding or subtracting 12 (so six flats is written as six sharps). Invalid input returns None.

Why this case matters

Part extraction must print a transposed key signature consistent with the transposed notes.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
oracle 0	`9`	`-3`	Failed

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