When we ( husband and I ) were looking for our apartment, one of the apartments we looked at ( conduit Rd, an old building, can't remember the name) had a 'music room'. That is a specially soundproofed room with electrical outlets, even a layers floor to resemble some kind of stage within a small room, but not too small. Usually the the walls are carpeted or lined with another type of soundproofing material.
Hope this helps. If you are not used to 'Studio' design, I recommend that you view the room.
N.B. We didn't choose the apartment viewed ( didn't like the 'leather' floor tiles, too much hassle to clean) .