Table of Contents

Pitches and enharmonic spelling

Celeritas represents pitch as MIDI numbers, and MIDI numbers are enharmonically neutral. Understanding that — and where spelling does live — avoids most surprises.

Pitches are MIDI integers

A pitch is an int: middle C is 60, and each semitone is ±1. The number encodes which key on the piano, not how it's spelled. MIDI 61 is the black key between C and D — whether you call it C♯ or D♭ is a notational choice the number doesn't carry:

Console.WriteLine(MusicNotation.ToNotation(61));                    // C#4
Console.WriteLine(MusicNotation.ToNotation(61, preferSharps: false)); // Db4

Both spell the same pitch 61. This is deliberate: analysis (chords, keys, intervals) works on pitch classes 0–11 — 61 mod 12 = 1 — where C♯ and D♭ are by definition the same class. Asking "is this chord major?" never depends on the spelling.

Parsing accepts either spelling

MusicNotation.ParseNote reads scientific pitch notation with sharps (#), flats (b), or the Unicode accidentals ♯/♭, and maps enharmonic equivalents to the same number:

Console.WriteLine(MusicNotation.ParseNote("C#5"));   // 73
Console.WriteLine(MusicNotation.ParseNote("Db5"));   // 73  — same pitch

Cross-octave spellings land in the octave you'd expect: Cb4 is B3, B#4 is C5.

Rendering back: sharps by default

Going the other way, the engine renders a spelling, and the default is sharps:

var pc = PitchClass.FromMidi(66);          // pitch class 6
Console.WriteLine(pc.Name);                // F#
Console.WriteLine(pc.ToName(preferSharps: false));   // Gb

The limits — and when spelling matters

Because a pitch is just a number, the engine cannot distinguish a note spelled C♯ from one spelled D♭ — that information isn't there to recover. For the engine's job (fast symbolic analysis and generation) that's the right trade: it keeps pitch comparisons integer-cheap and analysis spelling-agnostic.

Where correct spelling is a first-class concern — engraving, key-correct accidentals, distinguishing an augmented second from a minor third on the page — that's notation rendering, which belongs to a score layer on top of the engine (see the notation-interop direction on the roadmap), not to the pitch numbers themselves.

See also