I haven't tried to use digital recorders for music, but I've tried to use them for my job, and I hate them. The ones that I've tried don't pick up sound very well, and after you erase and record a few times, things start getting really garbled. Maybe high-end digital recorders would be better, but I can't recommend a low-end one.

I always end up going back to a high-quality tape recorder with an external mic. They're much more sensitive and record much more clearly. Here's the one I use and have recommended to other folks in my business. To be honest, I haven't tried to record music with it, but I don't see why it wouldn't work as long as you're just using it to get ideas down, http://www.amazon.com/exec/obidos/ASIN/B00008WIX3/thebookwyrm.