PSG instrument editor

The instrument editor for PSG (SMS, MSX, and other TI SN76489 derivatives) consists of these macros:

Volume: volume.
Arpeggio: pitch in half-steps.
Duty: noise mode.
- 0: short noise, preset frequencies.
- 1: long noise, preset frequencies.
- 2: short noise, use channel 3 for frequency.
- 3: long noise, use channel 3 for frequency.
Panning: output for left and right channels.
Pitch: fine pitch.
Phase Reset: trigger restart of waveform.