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Chord.Parse reads "-"/"+" alteration signs as chord quality: "C7-9" becomes Cm9, "C7-5" becomes Cm7, "Cmaj7-5" becomes CmMaj7, "C7+9" becomes Caug9 #345
Description
What's wrong
Lead sheets often write an alteration as - or + after a number:
C7-9orC7(-9)means C7♭9C7-5means C7♭5C7+9means C7♯9
The parser only recognises b, ♭, # and ♯ as alteration signs (ConsumeTensions, Chord.cs:288-312; ConsumeFifthAlteration, Chord.cs:315-329). Instead:
- a
-anywhere in the body is read as a minor third (IsMinor,Chord.cs:381-384,body.Contains('-')); - a
+anywhere is read as augmented (DetermineQuality,Chord.cs:360).
Parentheses are stripped first (Chord.cs:66), so the explicit form C7(-9) is misread the same way.
Reproduced
These results come from running each input through the built library at 7167117:
| Input | Result today (ToString / tones) | Meant |
|---|---|---|
C7-9 / C7(-9) |
Cm79, [0,3,7,10,14] |
C7♭9, [0,4,7,10,13] |
C7-5 |
Cm7, [0,3,7,10] |
C7♭5, [0,4,6,10] |
Cmaj7-5 |
Cmmaj7, [0,3,7,11] |
Cmaj7♭5, [0,4,6,11] |
C7-13 |
Cm713 |
C7♭13 |
C7+9 |
Caug79, [0,4,8,10,14] |
C7♯9, [0,4,7,10,15] |
Each input is parsed as a different chord rather than rejected. In the ♭5 cases the alteration is lost entirely.
Suggested fix
- When
-or+directly follows a digit (so not at the start of the body), read-5/-9/-13asb5/b9/b13and+9/+11as#9/#11. Do this before the quality is decided. - Then make
IsMinorlook for-only at the start of the body. - Keep the existing readings of
C-,C-7,C-9(minor ninth),C-7b5,C+,C7+andC7+5.
Rejecting these spellings would also be acceptable; misreading them is not.
Acceptance criteria
- Each row in the table produces the "Meant" tones and round-trips.
C-7,C-9,C-7b5,C+,C7+andC7+5are unchanged.
Activity
matt-edmondson commentedon Sep 30, 2026
Triage
C7-9,C7-5andC7+9are standard lead-sheet spellings, and today they parse as a different chord with the wrong tones and no error. The scope is limited toChord.Parsein the Music package, but this is the most user-visible of the current Chord parser bugs.Semantics.Music/Chord.cs, inIsMinor(381-384,body.Contains('-')),DetermineQuality(360,+handling),ConsumeTensions(288-312),ConsumeFifthAlteration(315-329) and the parenthesis stripping at line 66.Cm7#5/Cm+read as augmented) touches the same minor and augmented detection, so the two should be fixed together. Chord.Parse accepts quality characters in any order and any number: "C7M", "C57", "C77" and "C7m" all parse as C7 #346 (quality characters in any order) changes the same leftover and quality checks. Chord.Parse stacks the natural 9th/11th under an altered one: "C13#11" sounds both F and F#, "C13b9" both Db and D #341 (altered tensions stacked on natural ones) is also inConsumeTensions. Chord.ToString() writes an altered tension straight after the root: "C(#11)" prints as "C#11" and reparses as a C# dominant eleventh #336 and Chord round-trip breaks for a seventh with add11/add13: "C7add13" prints as "C713", which reparses as C13 with a 9th and 11th #300 are the ToString round-trips, and the acceptance criteria here need round-tripping.-/+that follows a digit intob/#before the quality is decided is the smallest change. PinC-,C-7,C-9,C-7b5,C+,C7+andC7+5with regression tests before changingIsMinor.Generated by Claude Code
matt-edmondson commentedon Sep 30, 2026
Covered by #360, which redesigns this bug cluster as a whole. Implement it through that issue rather than individually.
Generated by Claude Code
[minor] Redesign chord symbols; fixes #300, #322, #336, #340, #341, #344