I suppose the thinking is that extra thick walls with stucco will produce a good sonic environment, you know, a cool place to make a lot of noise. Maybe. Until it leaks out the ceiling and/floor.
What about insurance? What about have you ever built anything at all before? Planning on getting a permit to build, or is that only the American government that fleeces it's people:) When "new/old gaining new ground due to rising construction costs" ideas come along people resist...people that you need to play along.
Why are you thinking of building a strawbale room? Because it looks like a much cheaper way to go?
The "R" rating on this type of "wall" structure is high...that's good! But sound will penetrate under a raised floor or out the ceiling faster then you can say "you got any morra those pink thangs?"
Do you have a size in mind? I got one word for ya....rectangular! Wait, I got another word, planning. ****, here comes another one, budget!
How much are you willing to commit to see this project to the end AND how important is it to you that it be a baled construction? Would a room in your existing home be better suited with modifications to the sonically weak areas, e.g. walls, ceilings, doors, floors, penetrations in walls, AC vents?
I live in a high density suburb so I am thinking about the noise impact and the thick walls and absorbant nature of the straw. The economics and planning approvals are less of an issue. I have read about straw bale studios that are supposedly successful but have no experience with them.