Under Page 5 of the Commands for MML (Music Macro Language) page, the Instruments section states that instrument IDs numbering @256 and above correspond to that of the BEEP IDs (photo for reference):
Upon trying this out, I found:
- Random sounds exist beyond @255 with no exact correspondence to BEEP IDs
- In certain ID's (but not all), changing the pitch and/or octave changes the sound produced entirely
- Certain IDs correspond to the BGM sounds rather than the BEEP sounds as stated, and
- No order is stated in the instructions, making it confusing to find a particular sound.