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Chord round-trip breaks for a seventh with add11/add13: "C7add13" prints as "C713", which reparses as C13 with a 9th and 11th #300
Description
Activity
Triage
- Category: Bug
- Priority: Medium. It breaks the parse/format round-trip.
ToString()of a valid chord reparses as a different chord with extra tones, so any caller that stores chords as text silently corrupts them. Only seventh chords withadd11oradd13are affected. - Area / suggested assignment:
Semantics.Music/Chord.cs(AppendTensions, lines 598-622) andChordRoundTripTests.cs - Duplicates: none found among open issues in the org. It is a regression surface from Read C69, Cadd11 and Cadd13 as added tones, and reject leftover text [patch] #293.
- In progress: no matching open PR
Notes: The suggested fix is right: emit the highest contiguous natural stack as a number, then
addNfor the rest. Keeping #293 is better than rejectingaddNagain. Add the four failing inputs to the round-trip corpus first, so the fix is test-driven.
Generated by Claude Code
Covered by #360, which redesigns this bug cluster as a whole. Implement it through that issue rather than individually.
Generated by Claude Code
What's wrong
Since #293 (ad24784),
Chord.Parseacceptsadd11andadd13after a seventh. For example,"C7add13"parses as a dominant seventh with tensions{13}only, and a check gives tones[0,4,7,10,21].The formatter can't write that chord back.
AppendTensions(Semantics.Music/Chord.cs:598-622) writesaddNonly when there is no seventh. With a seventh it writes the highest natural tension as a bare stacked number ("13","11","9"). On reparse,ApplyExtensionsexpands13into 9 + 11 + 13.Observed (scratch app referencing Semantics.Music)
ToString()C7add13C713[0,4,7,10,14,17,21]vs original[0,4,7,10,21]C7add11C711C9add13C713Cmaj7add13Cmaj713The round-trip corpus (
ChordRoundTripTests.cs:12-18) has no seventh+addN case, so the tests don't catch this.Suggested fix
When there is a seventh:
9, 9+11 →11, 9+11+13 →13.addN. For example,{13}gives7add13and{9,13}gives9add13.The alternative is to reject
addNafter a seventh in the parser again, but that would undo #293.Acceptance criteria
C7add13,C7add11,C9add13andCmaj7add13are added to the round-trip corpus, and each one round-trips to equal tones.