Function instrumentTransposition

instrumentTransposition(instrument: TransposingInstrument): SpelledInterval
The interval a transposing instrument sounds at, measured from what it reads.

This is the table's own direction: the answer descends for an instrument that sounds below the printed part, which is most of them. Applying it to a written pitch is toSoundingPitch, and applying it to a concert key is how a written key is read back as the key it sounds in.
Parameters
- instrument: TransposingInstrument
  A built-in instrument name, or an interval naming a transposition the table does not carry.
Returns SpelledInterval
The written-to-sounding interval.
Throws
If the value is neither a known instrument nor a spelled interval.
Example
```
import { instrumentTransposition } from '@libraz/libcantus';
instrumentTransposition('clarinetA');
// { number: 3, quality: 'm', semitones: -3, descending: true }
instrumentTransposition('piccolo');
// { number: 8, quality: 'P', semitones: 12, descending: false }
```
- Defined in src/theory/transposition/index.ts:147