Can I wire my entire music studio on a single circuit?
I don't have the reputation to comment so I'll jot this down as a partial answer.

Install 12A wire in the building You are outfitting an accessory building to do music production; not just lighting a room. By July it will occur to you that you need a small AC window unit and a mini-fridge. Don't skimp on the wire now.

Strongly consider installing a sub-panel This allows you to run separate circuits for lighting and electronics. Not to mention a 20A circuit for your future wet-bar.

Think about lightning risk; think about ground loops If lightning strikes this building what is the path to earth? If you ground the sub-panel locally you can introduce a ground loop. Especially since you probably have a mix of grounded electronics (computers with 3-prong plugs) and un-grounded musical equipment (amps with 2-prong plugs). I suspect the best approach will be to avoid a separate local ground and tie back into your main house ground. So make sure your grounding conductor back to the house is of sufficient gauge. I don't know if putting the dimmers on a separate energized wire from your wall outlets will help avoid magnetically induced hum. If it does, this would be one justification for running MWBC as others have suggested.