Control Room in home in open loft, verses garage?

Hello I'm new, having recently discovered this site and spending hours reading all the great advice. Here's a question for a home project studio, please: I'm considering building out one stall of my 3 stall garage that measures 18' long, 10' wide, and 8 to 12' tall, using as a template one of the small studio plans I've found on this site. However, I'm now wondering if it would work to put the studio in my upstairs loft. That's an open area, triangularly shaped with one side open to a large 22' height dining and formal living room. We have our 9' grand piano in the living room. Acoustically, what would be better for a control/mixing room? A properly constructed single car garage space, or an open loft, assuming no need to obtain isolation from the outside? Appreciate your ideas and advice, Craig

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