Oh I just remembered, the best example of Bill looping that I've ever heard is on "A Confederacy of Dances" from Einstein/Roulette. It's a compilation of downtown performances at Roulette by different people and starts off with an 8 min solo Frisell loop piece (If I remember correctly). Sounds like 3 guitars at once. I think Roulette has a web page, you can order it from there.