I have no personal experience with ground-up construction, but know a few basics about acoustics that may help some.
First thing, consider using cement flooring (rather than plyboard) and cinderblock filled with sand for walls, rather than your more typical wood frame + siding/drywall/corrugate approach to sheds and so forth. More mass = less vibration, and helps isolate sound much better. Not sure about what an equivalent roofing solution would be on this scale.
If possible, avoid 90 degree angles in the interior space, which make standing waves easier to accumulate. Doesn’t have to be drastic, a slight trapezoid or parallelogram shape should help.
Lastly, maybe consider going windowless, or otherwise use double (or triple?) panes. Again, for sound isolation. Might be overkill depending on if your neighbors are decent and you actually have some reasonable space between one another. I’m operating from the assumption that neither are true.
That’s all I got. Good luck man, this will be a hell of an undertaking, but will feel awesome when you finish it!