Sorry you're having so much anxiety over this my friend.
I'd encourage him to see the University counselor about it and that there's nothing to be scared of at all. Have him explain to them what's happening and get some help. It shouldn't cost anything and is usually free. They can't typically write prescriptions for meds but the regular docs can and it will take a while for them to act anyway.

I'm not sure I can understand why you're so stressed about his academic performance. It really is his choice though obviously he's suffering his own dark time.
You said you need him to pass and don't know what you'd do if he didn't so without explaining more I'll take it you just really need him to for some reason. Also, even if you did know something about music, it would be unethical and most likely a violation of any honor policy at his school which could be an expulsion offense to do his work for him.

Maybe you could step back and realize that although it's something you really want and feel like you need, ultimately it's his choice what he does and why he does it. Try to isolate yourself and not let it trigger you (in this sense, triggering depression).

I'd really try to get him to talk to a college counselor or maybe even a prof. in the psych department.

Good luck my friend and remember to breath.

Chris