Listen room Insulation only

tsugury, excellent. I built my house in 1993 and there are vapor barriers everywhere including under the concrete in the basement. If you want to turn the garage into a listening room to keep the humidity down you'll have to close off the garage doors (they can always be added back), add a vapor barrier to the walls and ceiling and drywall everything. Breathing fiberglass is a very bad idea. The paper with also crackle with the music. Drywall was dirt cheap. Not sure what it is now but it will come back down.
It is a garage so, the building inspector may make you use fireboard. 

Might want to consider using this stuff - https://www.builddirect.com/blog/denim-insulation-the-good-and-the-bad/

The room will sound too dead. I've walked throughout my house after insulation in every wall and before the sheetrock, and it was dead. Everywhere you talked, dead. Music would also be the same.

YUP no sheet rock and just insulation, DEAD as a door nail. It would be BAD. Even a very thin sheet of construction poly vinyl or PVC or even 15 or 30 lb roofing felt over the top would liven it up a bit..

I've added to many rooms to forget how one day it was dead quiet, the next day with sheetrock being put up getting noisier and noisier.

Actually one room the lid was put on after the walls were remodified. That was interesting, with NO ceiling reflection, just a HUGE bass trap over your head..

Regards 

Thanks for the replies