Source: https://guthlabs.ai/docs/instruments/midi-note-number-note-name-converter/implementation/

instrument implementation / implementation-contract

# MIDI Note Number ↔ Note Name Converter implementation

A source-bound implementation contract for MIDI Note Number ↔ Note Name Converter; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t6-043

**Effect**: Computation or source lookup only

## Input and validation requirements

- 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.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "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."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/midi-note-number-note-name-converter/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/midi-note-number-note-name-converter/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/midi-note-number-note-name-converter/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche6/tranche6-results.json`