If by dev you mean editing, and not creating, then Audacity is pretty decent...

 

Would help if you specified the platform. Assuming its windows theres not a whole bunch of high-end freeware apps for audio production, you can try out many demos for free though which is always advisable for something like Sonar or Reason before you "buy" it.

What there are freeware apps of, are things like vst fx and instruments, but again you'll need a host app to use them. This however is freeware, but unless you come from a demoscene background i'm pretty sure most of you wont like it, it's a very popular multi-platform tracker called Milky Tracker.

I'm sure there must be other suggestions, sorry i cant be of more help on the freeware side of things, but my trade is music production so i'm pretty much working with high end expensive software