Om.

I recently purchased Walter White's Long Tones Accompaniment CD. It contains three 20-minute long tracks, each on a different key centre, so you can sit there and play a 20-minute long G (or C, or whatever). Duke Ellington's famous screaming trumpet player, Cat Anderson, advocated this excercise, and it still finds favour among many of today's top brass players.

It might seem unnecessary to have a CD to play along to but I think it greatly helps me keep focused on the exercise. The music's a bit 'new age' - I doubt I'd choose to listen to it for it's own sake - but it's really good for the long tones: very calming, and the ten bar chunks (play eight, rest two) keep you regular.

A couple of tips for an extra-zen experience:
- Turn off the lights
- Play through a nice reverb. I use Audioease's Altiverb, which means I can sit and play in a virtual Notre Dame Cathedral (or if you can practice in an actual cathedral, that's even better).
- Put on the iTunes visualizer, or kick off Soundstream - a screensaver (for OSX) which responds to sound input - psychedelic.

Oh, and btw, it helps your embouchure!