This arrangement of the first movement of Mozart's Symphony # 40 has no extreme registers
in the trombone parts (several Dbs in tbn 1, but the vast majority of tbn 1 stays below Bb).
 Although loaded with notes, the arrangement is technically quite playable (particularly
if taken a bit below tempo--it still sounds good a bit slower).  The challenge is endurance.
 If performed by a choir, this is not a problem--players can just spell eachother.
Since there are a lot of notes and not much rest, care has been taken to provide adequate
breath marks, and to avoid awkward leaps.  If endurance becomes an issue, it's a simple
matter to shorten this arrangement:  since it is sonata-allegro form, it is possible to end at
the conclusion of the exposition (bar 52).  This reduces the length to 1/3rd of the arrangement's
original length.  Or, for a longer arrangement, play the exposition through twice (common
practice in sonata-allegro form).  This is efficient, since players only need to learn the first
1/3rd of the arrangement.