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Chord.ToString() writes non-standard symbols: G9 → "G79", Gmaj9 → "Gmaj79", G13 → "G713", G7sus4 → "Gsus47", C6/9 → "C6add9" #358
Description
What's wrong
AppendQualityAndSeventh writes 7/maj7 first (Chord.cs#L590-L624). AppendTensions then appends the natural extension number after it (Chord.cs#L645-L688). The resulting "canonical symbol" is not something any chart uses:
| Parsed from | ToString() |
|---|---|
C9 / Cm9 / Cmaj9 / Caug9 |
C79 / Cm79 / Cmaj79 / Caug79 |
C11 / C13 / Cmaj13 |
C711 / C713 / Cmaj713 |
C7sus4 / C9sus4 |
Csus47 / Csus479 |
C6/9 / Cm6/9 |
C6add9 / Cm6add9 |
Progression.Parse("4/4 Dm9 | G13 | Cmaj9 | G7sus4").ToString() gives "4/4 Dm79 G713 Cmaj79 Gsus47". Section.ToString() and Arrangement.ToString() inherit the same output.
Parse(ToString()) still round-trips, and the round-trip corpus (ChordRoundTripTests.cs) compares only the parsed structure. Because no test pins the text, this was never caught. The type-safe factories spec calls the output a "canonical symbol (e.g. Cmaj7, C/G)" (spec L95-L153).`` A chart format meant for people should print what a musician writes.
Suggested fix
- When a natural extension number is emitted for a seventh chord, let it replace the
7: dominant7+9becomes9, andmaj7+9becomesmaj9. - Put
susafter the number:7sus4,9sus4. - Write a 6 with an added 9 as
6/9, whichChord.Parsealready accepts.
Coordinate with #300, which reworks the same AppendTensions branch for 7add13. That issue is about losing the round-trip; this one is the ordinary C9 → C79 case.
Acceptance criteria
ToString()returnsC9,Cm9,Cmaj9,C11,C13,Cmaj13,C7sus4,C9sus4,C6/9andCm6/9for the inputs in the table.- The round-trip corpus gains a text assertion,
Parse(s).ToString() == sfor canonical inputs, alongside the structural one.
Activity
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
matt-edmondson commentedon Oct 5, 2026
Triage
enhancement, but this is wrong canonical output)Semantics.Musicchord symbol writerC9,Cmaj9,C7sus4,C6/9, … print as themselves). Redesign chord symbols: one grammar for Chord.Parse and Chord.ToString (fixes #300 #322 #336 #340 #341 #344 #345 #346 #358) #360's sub-issue summary shows only 1 of 9 closed, though. PR Redesign chord symbols around a shared grammar #362 apparently didn't use closing keywords for the sub-issues, so Chord round-trip breaks for a seventh with add11/add13: "C7add13" prints as "C713", which reparses as C13 with a 9th and 11th #300, Chord.Parse reads "CM9", "CM11" and "CM13" as dominant chords (Bb, not B), and "CmM9" as a plain Cm9 #322, Chord.ToString() writes an altered tension straight after the root: "C(#11)" prints as "C#11" and reparses as a C# dominant eleventh #336, Chord.Parse reads "Cm7#5", "Cm#5" and "Cm+" as augmented chords with a major third (Cm7#5 comes back as Caug7) #340, Chord.Parse stacks the natural 9th/11th under an altered one: "C13#11" sounds both F and F#, "C13b9" both Db and D #341, Chord.Parse drops everything after the slash-bass note: "C/Gm", "C/E/G" and "C/Bb7" parse as "C/G", "C/E" and "C/A#" #344, 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, Chord.Parse accepts quality characters in any order and any number: "C7M", "C57", "C77" and "C7m" all parse as C7 #346 and this issue are probably all still open despite being fixed.Recommended next step: Check on
mainthatChord.Parse("C9").ToString() == "C9"(and the rest of the acceptance table), then close this issue and its siblings as completed, referencing #362.Generated by Claude Code
matt-edmondson commentedon Oct 26, 2026
This was fixed by d6116b6, which only closed the first issue it named. Checked on main at 7c693f4:
ToString()writesG9,Gmaj9,G13,G7sus4andC6/9. The old spellings (C79,Csus47,C6add9) still parse through the legacy reader.CanonicalExtensionSymbolsRoundTripWithTonespins this. Closing.Generated by Claude Code