Source: https://guthlabs.ai/docs/instruments/midi-note-number-note-name-converter/
instrument / verified-clean
# MIDI Note Number ↔ Note Name Converter
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Audio, Music, Photography & Color
**Tranche**: tranche-6
**Evidence ID**: t6-043
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The arithmetic is correct under the standard MIDI convention, but the specification needs an explicit note-name mapping, reverse-conversion rule, valid input ranges, and enharmonic spelling policy. Because these behaviors are ambiguous, the instrument requires review before being considered fully specified.
### Formula and scope findings
- The forward formula is standard for integer MIDI note numbers: note_index = MIDI % 12 and octave = floor(MIDI / 12) - 1, with MIDI 60 = C4.
- The note-index-to-name mapping is not specified. A canonical spelling convention is required; the vectors below assume sharp spellings: C, C#, D, D#, E, F, F#, G, G#, A, A#, B.
- The reverse conversion algorithm is not stated. It should be MIDI = 12 × (octave + 1) + note_index.
- The supported MIDI-number domain is not stated. Standard MIDI note numbers are integers from 0 through 127; values outside that range should be rejected unless an extended domain is intentionally supported.
- The accepted note-name syntax and enharmonic aliases are not specified. For example, C#4 and Db4 represent the same pitch but require an explicit policy.
### Unit assumptions
- MIDI note numbers are dimensionless integer values in the standard range 0–127.
- Note names use scientific pitch notation with an integer octave, such as C4 or G#5.
- The octave convention is MIDI/scientific pitch notation: MIDI 60 = C4 and MIDI 69 = A4.
- The canonical output uses sharps rather than flats: C#, D#, F#, G#, and A#.
## Boundary hardening
### Recorded hazards
- Reject non-integer MIDI inputs, MIDI values below 0, and MIDI values above 127 unless the product explicitly supports a nonstandard range.
- Avoid language-specific remainder behavior for negative values; validate the MIDI range before applying modulo.
- Define whether note names are case-sensitive and whether formats such as Bb4, DB4, C♭4, or B#3 are accepted.
- Define behavior for enharmonic spellings and normalize aliases to one canonical output spelling.
- Ensure octave -1 is formatted unambiguously as C-1 rather than being confused with a negative note number.
- Do not silently clamp invalid inputs or return a plausible-looking result for malformed note names.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"midi_number": 0
},
"expected_outputs": {
"note_name": "C-1",
"note_index": 0,
"octave": -1
},
"working": "note_index = 0 % 12 = 0. octave = floor(0 / 12) - 1 = 0 - 1 = -1. Index 0 maps to C, so the result is C-1."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche6/tranche6-results.json`