I took a second, in-depth look at the trombone part. I totally disagree with Nightingale - the part, though quite challenging and a long blow is completely playable. A good undergrad trombonist should have little trouble with it. I know I certainly wouldn't, and I'm a jazz player.
Re: exceedingly high tessitura : The highest note is a Bb (right?) and perhaps I've spent too much time reading jazz ensemble lead parts, but anything lower than a D doesn't warrant a second glance. Stamina may be a problem, but again - where you're not hanging out constantly in mid treble-clef range, I doubt it'll be an issue. Perhaps a bit more space somewhere - it
will be a long, hard blow, but that's for the trombonist to deal with.
Re: clefs, he's right. I suppose.
Personally, I'm more comfortable with treble (that's just me with a jazzers training - never learned alto/tenor clef). I don't feel A's, Bb's really
need a clef change anyway. I wouldn't be upset to see it all in bass clef. But, whatever.
I just don't feel it needs any simplification...
