Aside from simply learning/improving/maintaining good fundamental trombone skills, learning to play in a jazz ensemble is largely a function of knowing what it is supposed to sound like and developing the EARS. The ears are the only thing that matter in jazz.
We often tell aspiring improvisers that the primary, numero uno thing they need to do is to put the horn away and LISTEN to recordings of great jazz, to submerge themselves in all kinds of jazz music — big band (Ellington, Basie, Glenn Miller, Thad Jones/Mel Lewis, Buddy Rich, Maynard Ferguson, Kenton, Woody Herman), trad/swing (Louis Armstrong, Jelly Roll Morton, Gene Krupa, Tommy Dorsey, Fats Waller, Jack Teagarden, Lester Young, Benny Carter, Billie Holiday), Bop/Post Bop (Charlie Parker, Dexter Gordon, Sonny Stitt, Sonny Rollins, Clifford Brown, Thelonius Monk, Dizzy Gillespie, Freddie Hubbard, J.J. Johnson, Lee Morgan, Frank Rosolino, Bud Powell), Modern/Free/Post Modern Jazz (Miles Davis, Bill Evans, John Coltrane, Wayne Shorter, Horace Silver, Herbie Hancock, Chick Corea, Dave Holland, Ornette Coleman, Archie Shepp, Cecil Taylor, Art Ensemble, Charles Mingus, Wynton Marsalis, Jerry Bergonzi, Chris Potter, George Garzone, Nick Payton, Kenny Werner, Danilo Perez, John Scofield, – the list of greats today gets far too numerous to effectively thumbnail…).
And most significantly of all today: the great Elvin Jones.
So there is an initial outlay here of money (to Aebersold Jazz or Mosaic or Amazon or Barnes & Noble) or time and energy (going to the library). Much as the aspiring novelist MUST immerse him/herself in the great literature of the past, the aspiring musician CANNOT get past the profound, primary step of committing the great music of the past to his or her psyche.
But immersing one’s self in great live and recorded music is not merely a critical task for the improviser – it is also of primary importance to the big band section and lead player. One simply HAS to have the sound of a jazz line being played with great, swinging time and inflection completely ingrained in their head in order to be able to play in the big band style. So I cannot stress this step enough for ALL musicians learning to perform in a jazz setting.
Next, we can get the horn out again. Start to play along with some of the simpler jazz recordings we have heard, such as Miles’ solos on his “Dig” and “Kind of Blue” CDs, any Louis Armstrong or Harry “Sweets” Edison or Kenny Dorham or Paul Desmond (1950/60s Dave Brubeck) solos — there are also a variety of historical trombone figures whose solos are, relative to the other instruments of the period, reasonably accessible to the novice jazz trombonist: Trummy Young, Jack Teagarden, Lawrence Brown (Ellington trombonist) and J.J. Johnson. Pay attention to emulate the sweet subtleties of each player, the length of the notes, the character of the articulation when they play a line.
As one’s technique progresses, one can move on to the more advanced Bebop and Modern players.
Of course, the improviser MUST spend a great deal of time actually playing jazz with a live combo or with play-along CDs, such as the Jamey Aebersold Play-A-Long Series. This is where you learn to actually find ways of applying what the ears have picked up from all of this intense listening in one’s own playing.
And one last, vast, fundamental jazz skill is the ability to read chord changes and standard notation in the jazz genre.
Jazz notation is a whole level of literacy unto itself. Learning simply what chords are and standard scale choices associated with chord symbols comprises an entire, two-semester class – but a good place to have all this material in one comprehensive reference is in Dan Haerle’s excellent The Jazz Language.
In order to develop your ability to read standard notation jazz charts, it is good to bug your band director to get some copies of trombone parts to jazz band charts to take home and practice. But don’t just pile into these pieces! Remember how the great musicians you listened to sounded when they played those lines? It is a good idea when playing these parts to periodically stop, walk to the stereo, and listen again to how Hank Mobley or Art Farmer sounded when they played simple, swinging jazz lines. Push yourself to match the relaxed and smooth style of these greats – the ability to play in this manner is a skill which will benefit you tremendously in any ensemble performance situation for the rest of your life.