Bert, you are correct in wondering about dead spots. There were many in the dome. I remember moving to a place about 10 feet from the center spot where I discovered that I couldn't hear my own guitar! It was as if the sound was sucked out of it. Truly an odd experience. But the "sweet spot" more than made up for it.

Some time back there was a label used to describe small rock bands: "garage bands". I always have wondered why the term was used derogatorily. The acoustics (or, rather, the echoes) are usually quite good. Les Paul and Mary Ford liked it so well that (at least, according to my sources) they tried to figure out how to reproduce it electronically. They decided, by experimentation, that a 1/5th of a second echo was most pleasing to their ears and so created or caused to be created a device to make that echo. This, I am told, was the birth of electronic tremolo.

The dome had no echo of that sort. Just instantaneous feedback - the good kind ;-)