We live one door down to the house that could be described as the house that backs up to Pandora's. We have a porch off our bedroom upstairs, and when we first moved in last September, I'd go out on the porch and listen to the music from Pandora's. It was barely audible, just a soft murmur of background music. It was really pleasant. That stopped shortly after we moved in, when these complaints started. The music had never been loud enough for us to hear when we were inside the house.
As for Saturday night, I never heard any music. Our upstairs air conditioner was broken, so I had the back doors to the porch open as well as all the windows. I heard nothing. My peace was only disturbed by the fireworks on the beach (the gunpowder smell was drifting into my bedroom) and the flashing lights of the three police cars at a nearby house.
With all this support, perhaps a campaign of visibility would help more than anything else. Come up with a slogan -- something like "I support live, local music" or "Keep Grayton Funn" with a musical design -- and make bumper stickers, yard signs, etc. Perhaps local folk/political sign painter Skunkape would volunteer his services...I'm sure with all the talented people in the arts community around here, a great design would be easy. I'll volunteer to put up a yard sign. I'm sure the visible support of neighbors would do much to further your cause!