LISTEN!
"In order to 'outflow' music, you need to 'inflow' music." – Phil Teele
Here are some links to seminal performances of trombone solo repertoire (yeah, there's a lotta Morceau Symphonique) and some other tidbits. I assume the performers are OK with these being online – if not, they may vanish. You'll need to click to see who's who. Enjoy! (Hopefully, these links will remain un-broken.)
Also, Branford Marsallis shares some wisdom here.
Also, Branford Marsallis shares some wisdom here.