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# AudioUnitParameterUnit.midiNoteNumber

A whole-number unit of measure corresponding to audio frequency.

```
case midiNoteNumber
```

## Discussion

Absolute pitch as defined in the MIDI specification. A standard piano keyboard ranges from MIDI note number 21 (for the A0 note) to 108 (for the C8 note), with MIDI note 60 corresponding to middle C (C4). The frequency for a given MIDI note number may depend on a tuning table.

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