I had the luck to acquire a license of the Neobitz "Neo Sound Builder" from Jeff Kurtz a few years ago.
The software allows to import 16bit mono .wav files and generate ADPCM-A sound files out of it.
After that you can export them into V1 and V2 roms + M1 driver rom + sound.h (contains ADPCM Sample commands).

https://www.facebook.com/media/set/?set=a.415692581788967.103107.221161891242038&type=3