Orchestral/Jazz tune. What do you think?

Hey, great job! I love the Jazz harmony and the voice leading sounds fine. I would say only at a few places the chords could have been less "blocky" but maybe it was intentional.

Structurally, I feel that the intro is a little bit too elongated. Then when you finally get into the tune, the problem is that well... there's not really a tune - you go straight into a piano improv. Be aware that all the pieces from this era are based on themes (just open the Realbook and you'll see).

It's still a lovely piece though, and you definitely got the vibe right.

 

First thing out of the gate, I agree with @Claude Ruelle about the intro, vibe, and harmonization/voice leading - so nothing to add there.
I think it would sound better without the winds (their performance wasn't that colorful or believable, and those lines would work fine in just strings or vibraphone...or even jazz guitar).
I couldn't sing the theme after 3 listenings, or anticipate the changes - maybe state the theme more explicitly.
Good sound on the simple kit with brushes and bass.
Also, generally like the piano improvisations too, nice playing.

So, some things to try if you're revisiting the piece:
Simplify the instrumentation
Give the accompaniment something to do (you have some moments of rhythmic activity which was refreshing to hear)
Make the form clearer (simple statement with violin melody, string pads, piano comping the chords...then take a solo on the keys, modulate & continue the solo, restate the melody in the keys with more colorful string interjections, and present a clear outro or tag ending)

Again, really nice sound & playing, I think it just needs to be a little clearer for the listener in parts. Thanks for posting & look forward to hearing new tunes or this one revisited. Cheers.