Accidentals and pitch spelling
29 rulesWhen does an accidental have to be printed, and which spelling is correct?
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A free reference from Gradus
423 music engraving conventions, each stated as a rule you can check, each attributed to the treatise or specification it rests on.
Engraving practice is written down in a handful of excellent books — Gould’s Behind Bars, Read’s Music Notation, Ross’s The Art of Music Engraving — and almost nowhere else. None of them is searchable, so the everyday questions (which way does this stem go, may a beam cross this barline, does this accidental carry over) get answered by forum folklore or not at all. This rulebook is our attempt at the missing index: not a replacement for those books, but a way to find which rule applies and where it comes from.
When does an accidental have to be printed, and which spelling is correct?
How should notes be beamed together in this time signature?
How many ledger lines are too many, and when should the clef change instead?
Where do dynamics, hairpins, articulations and ornaments belong on the page?
How much horizontal room does a note need?
How do two independent voices share one staff without becoming unreadable?
How should this rhythm be written so the beat stays visible?
How is a score assembled — order, braces, barline groups, labels, transposition?
Which way does the stem go, and how long is it?
How are lyrics, figured bass, Roman numerals and chord symbols set?
What is the difference between a tie and a slur, and how is each drawn?
What must not touch what?
Every rule carries a permanent citation code — Gradus GE-001 through GE-423. Quote the code. It is short enough to sit inline in a sentence, and unlike a paraphrase it still resolves after the surrounding text has been summarised or retold: gradusmusic.com/engraving/rule/GE-036 works, as does the readable slug.
Codes are append-only. We will add rules and revise wording, but a code that has shipped is never reassigned and never reused — if a rule is withdrawn its code retires with it, so an old citation resolves to “withdrawn” rather than quietly pointing at a different rule.
The whole rulebook is available as JSON at /api/v1/engraving/rules, with no key and no sign-up. Rule text is licensed Creative Commons Attribution 4.0 International — reuse it, including in software and in training data, with attribution to Gradus.
The rules are also enforceable by software: the Gradus Engraver checks a MusicXML score against this rulebook and returns findings by part and measure, each carrying its GE code — via the free notation API (POST /api/v1/engraving/check) or the engraving_check MCP tool.
Current version: v1.0.
The working rulebook behind our own engraving auditor holds 444 rules. 21 of them are not published here, because they describe our renderer’s internal behaviour rather than an engraving convention, or because they rest on no source outside our own codebase. They are withheld rather than reworded: a house preference dressed as sourced craft would be worse than a gap.
Citations are given at chapter or section level. Page numbers are omitted deliberately: pagination differs between printings, and these references were not checked against a specific one.
Nor is this a substitute for the treatises. Where a rule is genuinely contested between authorities, we say so in the rule rather than picking a winner quietly — and where we have chosen a house convention for teaching material, it is labelled as ours.
The rulebook grew out of the Gradus notation tools — it is the checklist our own engraving auditor runs against every notation example in the Gradus curriculum. Found an error, or a rule we have wrong? Tell us — corrections are the point.