Comment by miffe
If you want something more advanced, check out Furnace tracker. It supports nearly every 8/16 bit sound chip. And you can combine them in the same song.
So if you ever wanted to do a track combining a Mega Drive with a NES; it is possible.
And for people like me who suck at using trackers, they provide a lot of musics using each chipset so that you can see how it works. It's really amazing.