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[patch] Spell the raised seventh above a flat seventh as #7, not a lowered tonic - #406
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…wered tonic Scale.DegreeOf broke the chromatic tie toward the flat spelling even when the flat candidate only existed by wrapping round the octave, so G# in A aeolian came out as degree 1 lowered and Key.RomanNumeralOf labelled the minor-key leading-tone chord "bi°". When the flat would wrap, the tie now goes to the sharp spelling of the last degree; every other tie still prefers the flat. Fixes #304 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_0176ydtLncnCjKchHXEPCh7H
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This was referenced Oct 9, 2026
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Fixes #304
What changed
Scale.DegreeOfspells a chromatic pitch against its nearest scale neighbours and breaks a tie toward the flat. Above the last degree there is no upper neighbour, so the flat candidate wrapped round the octave to degree 1. In every flat-seventh mode, semitone 11 then came out as a lowered tonic: G# in A aeolian was(1, -1), andRomanNumeralOf(G#dim)returnedbi°.Now, when the flat spelling only exists by wrapping, the tie goes to the sharp spelling of the last degree. A strictly closer flat still wins, and every other tie still prefers the flat, so major-key bII, bIII, bVI and bVII don't change.
Tests
ScaleTests.DegreeOf_RaisedSeventhAboveAFlatSeventhIsSharpSeven: G# in A aeolian is(7, +1)KeyTests.RomanNumeral_MinorLeadingToneChordIsSharpSeven:G#dimin A aeolian andF#dimin G mixolydian both give#vii°KeyTests.RomanNumeral_MinorLeadingToneChordRoundTrips:RomanNumeralOf→ChordFromRomanNumeralgives backG#dimWith the
Scale.cschange reverted, the first two tests fail. The round-trip test passes either way and is there as a guard. The existingDegreeOf_ChromaticPrefersFlatOfUpperDegreestill passes. The fullSemantics.Testsuite passes on net10.0 (1483 passed, 8 skipped).🤖 Generated with Claude Code
https://claude.ai/code/session_0176ydtLncnCjKchHXEPCh7H
Generated by Claude Code