The NGPC dev kit is available and it includes a complicated to use but functional sound tool you can use to track. I can't find it right now but I know it is out there somewhere, if only I remembered its name... I may even have it in a backup but I am away from home and can't check this. Also I think Ivan Mackintosh had made one and also there's a MOD>NGPC converter somewhere.
The NGPC sound is a lot clearer than that of other portables available out there, definitely worth using rather than a shitty game boy or game gear.