You could probably call my shed the smallest music studio space in the UK, being only 5'6" x 4'. It is a great little space to write, practice and record music away from everyday life in the house. I have tried to make a small space as practical and inspiring as possible, with a lot of my musical gear at hand, guitar and microphone leads all on hooks above the window, with a great working and listening space.
This is very much a work in progress, the shed having only been built in the last few months. I am in the process of trying to add a degree of soundproofing, although bar vocals (and I've got a loud voice!) volume is not really a big issue.