Music is your hobby and you want to practice with your band. The only available place that you can think of is your garage but you also have neighbors that must not be disturbed while you are practicing. The only solution to use your garage as a music studio is to soundproof it or build a small studio in one corner of the garage. For this you need to use two existing garage walls and build another two new walls on an angle to improve the acoustics of the studio.
After measuring the angle you will have to anchor sole plates to the garage floor and frame the first new wall. After finishing the framing for the second wall and adding a door to this one you have to insulate the garage walls to help deaden the sounds. Next you will hang drywall on the new walls and patch the seams. The final layer of sound-deadening material will be applied to the walls and to the ceiling. This layer is made of some secondhand carpeting. After applying these carpets you can cover them with some strip boards pinned onto the wall with nails.
This is a brilliant idea. Your procedure to make the place sound proof is awesome. The studio you have shown in the image doesn't looks like a garage. Amazing work done by you.