A fantastic fantasy organ

I was walking north through backyards in Uptown. I came unto a garage with a sod roof. After climbing down into the front yard many people showed up all at once in cars or on foot. It seemed they were gathering after they had been together at another event, and they assumed I was part of their group. They went inside, I continued orth.

I was inside a keyboard store about where Heartbreaker's or McDonald's actually is on Hennepin. There was a preposterous organ with hundreds and hundreds of square keys arranged in a 3D sculpture that resembled a miniature rendition of the Alps or a microscopic view of some sort of bacteria - the pattern was almost like a Mandelbrot set. Some of the keys stuck up higher that their immediate neighbors and I found these sounded right when played together as I tinkered with it.