Really like this one. Very ambitious and texturally very nice. My favorite part was the horn section stabs. One thing about jazz though, especially in this swing-like style, the piano rarely holds chords. Because the bass is holding down the core of the harmony with the walking bassline (the core being the root and quality) the pianos main role is to fill space and add extensions. This means that the piano usually plays quite rhythmically and doesn't have to fill out all the notes of the chord. The good news is that this unlocks a whole new world of voicings when the function of the chord isn't a priority.
Music Motif Challenge » Entries » Song That Maybe Plays When Things Potentially Get Kinda Jazzy? Perchance?
Jazz theory is super fun to learn and it can be applied to any genre or area of music. I've been studying it for around 2 years now and still have huge gaps in my knowledge.
If you plan on writing more jazz in the future, I would reccomend listening to some classic records and paying attention to what each instrument is doing. Just like any genre, that is the best way to learn how to write it. Listening. The classic Miles Davis quote is "You have to know the rules before you break them" and that is very true too.