My favorite "ambient" release of Tibbetts is "Big Map Idea." I remember when I first came across his "Yr" album while in college; back then, it was a self-released LP on his Frammis label. He was kind enough to write back to me.
I think Safe Journey
also has some nice ambient moments to it. My intro to Tibbetts was also Yr
. I bought the LP at a used record store, I was going through the under dollar bin when I came across this album. I remember reading a pretty good review of it in some magazine that summer, so I took it out and gave it the once over. It had never been played, hand written on it was "promo copy" with dinosaur stickers. The price was 10 cents, no brainer, best 10 cents I ever spent.
One extremely ambient ECM CD I'd recommend is Stephan Micus' The Music of Stones, which, is surprisingly very drone-like and was recorded in a cathedral, IIRC.
I have that on CD, haven't listened to it in years but I remember enjoying it. I'll have to dig it out and give it a listen again.
BTW, still listening to that Jon Hassell bootleg, trying to catch some mojo for next months gig.