"a bit TOO simple in one way: you autoplay and loop MIDI files on each page."

That WAS the Design Intent. True, some don't like that.... actually - that is not on every page - I ran out of usable files long before that. They are on various 'main' pages.

"Unfortunately opening a linked page in a new window or tab doesn't turn the old page's music off"

Didn't use to do that - but then it was written years ago, and SW has changed since then....