I'm guessing that, of all the tunes on Backatown, "Where Y'At" is probably the band's favorite tune to play. Just listen to any live version, and you'll notice that the arrangement can take many shapes. Because of its flexibility, "Where Y'At" is a energetic and powerful tune for any situation.
The overall harmony is F minor, specifically the F minor pentatonic scale. Yet, notice how the horn melodies work outside the chord to build the harmonic shape and resolve the phrase back within the chord. As is the style of New Orleans funk rock, the "melody" is really in the guitars, the ascending and descending pentatonic riffs, while the horns provide the counterpart.
During the solo, the harmony becomes a b6-b7-i chord progression that is only used in this middle section of the song. Because of the natural energy of the progression, it sets the trombone solo apart from the rest of the tune and "turns it up to eleven." It's an interesting and effective compositional technique.
The solo itself may be a good exercise to work on playing in the upper register. It's very melodic and the fast rhythms will make you relax your throat and rely on your air support. But don't strain on this solo, pick out only a few phrases to develop. You can't play all day on those high C's (Arrrrgh, matey!). And those high F's should only be a product of energetic playing; you really should be hearing AND feeling those notes before you try to squeak 'em out. But remember to have fun with it.
SPECIAL THANKS to JTM, Noah Goldstein, Dor asaf, JR, and andy anynonomous for your comments!
Here's a YouTube video from Trombone Shorty's official channel.
Recommended Reading: Exercises and Etudes for the Jazz Instrumentalist: Bass Clef Edition by J.J. Johnson. Published by Hal Leonard.