I have my music room in a basement and IMO you only need to sound proof the ceiling and whatever is above ground because no sound is going to penetrate concrete and dirt. Acoustic treatment is a science that I have no expertise with but I do know that eliminating standing waves is very important.
This is a poured concrete foundation wall that I framed with 2x4s 16 in on center. And then filled the bays with rockwool insulation. And then I used landscape weed fabric and staples to cover it.. The weed fabric is what goes in garden flower beds.. it's pretty inexpensive and available at all the home improvement stores.. lowes home depot.. this works great to stop the echo and feedback from sound waves bouncing off a concrete basement walls. I bought a tapestry of guitar amps and stapled that over the top.. and I put some guitar wall hangers up on the studs. As well as hung some of my rack gear as well. My room is on the small side so floor space is at a premium.
Here is another picture of the same concrete wall.. I didn't frame it all the way into the corner because I have the drums setup in the corner of the room under the stairs and it's a bit tight already behind the kit. So I just used some 3/4 inch thick Styrofoam insulation behind the drums. If you look on the walls and ceiling you can see .I made a bunch of sound panels out of the same rockwool with ferring straps and covered them with the same weed fabric. I hung these home made panels on the celing and on the sheetrock walls.. for the concrete floor I put down a layer of moisture barrier paper like they use under engineered flooring.. and covered the paper with a cheap piece of carpet.. all this stuff is pretty cheap to purchase and with a little time and elbow grease will save a lot of money as apposed to buying professional sound treatments. And it really does make a huge difference in how the room sounds.. my band is 2 guitarist...bass player.. and acoustic drums in a small room and it sound great and records well ..
1 last pic of the home made sound treatment panels on the sheetrock wall.. these made a huge difference in the sound of my small studio/ live band rehearsal/ practice room..
Another thing I did was to run a new / separate 20 amp circuit from the electrical panel to the room and everything in the room is plugged into that 20 amp circuit. All the Amps. Rack gear. Guitar pedals..PA .. mixer desk.. everything is on the 1 circuit.. and everything is in the on position.. so I just need to flip 1 switch on a terminal strip and everything electrical comes on at once . Everything is on just 1 circuit which eliminate ground loops and all the hum and buzz that can happen when you use multiple circuit in the house for your amps.. hope this helps anyone setting up a music studio.. it's not a traditional stage type setup.. it's more what I would call a circle setup.. where all the amps are against the walls pointing in to the room. But it works great.. everyone can hear each other and you can play a full band at reasonable volume levels... I have everything mic up and use compressor/ gates on all the mics and get pretty darn good results recording a full band in such a small room.. hope this helps..
