FA-81159 / Music interval and transposition theory / Member archive

Written key signature for a transposing part: impossible flat concert keys accepted · case 04

A concert signature of -8 flats is accepted and transposed instead of rejected.

Member previewVariant 4 · 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 7	`5`	`null`	Failed

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