Listen room Insulation only

Be the same as any other exterior wall. Interior walls are sheetrock screwed to studs. Exterior walls are the same only with insulation between the studs. A garage being unheated space is treated as exterior, hence the insulation. 

It will definitely reduce the sound reflections you’d get if the walls were sheetrocked. It might result in a 'deader' space.

going to try it and report

Do youself a favor and cover it with polyethylene. This will keep the small particles from escaping and possibly causing resperatory issues. IF the paper backing is stapled over the studs is fastened over the face of the stud rather than inside it, you may be alright w/o the polyethylene. 
I am a builder and always noticed a tickle in my throat until the insulation was covered

Addendum

IF the paper backing is stapled over the studs is fastened over the face of the stud rather than inside it, you may be alright w/o the polyethylene.

should read

IF the paper backing of the insulation is fastened over the face of the stud rather than inside it, you may be alright w/o the polyethylene.

Nothing you can do will make a garage sound good.Good luck though.

Is it a heated garage?Does it stand alone?  If it has a common wall with the house you don't want another vapor barrier with a wall that already has one. This would create moister problems. Need more details!

This vapor barrier has been a source of controversy for 50+ yrs or more. If you buy into the idea, then use Tyvek. It may be cheaper. My whole point is that you do not want to be breathing the dust from fiberglass  insulation for long periods of time. It needs to be covered for habitation

Don't use fiberglass.  Roxul is awesome stuff.  I totally agree with artemus and cover the walls with Tyvek.  Not only will it stop fibres, it will keep everything cleaner and look finished.  
You do realize the sound will really bleed outside...?

This vapor barrier has been a source of controversy for 50+ yrs or more ? .https://www.certainteed.com/insulation/resources/do-i-need-vapor-barrier .Where is the controversy? this is standard buliding practice!

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