Welcome to the world of "Super Funk Rock." This tune is pretty simple and straightforward, and the solo remains diatonic as well. But what makes this an amazing solo are the funk and rock qualities: rhythm and power.
Most of the rhythm for this solo is based around the steady use of sixteenth notes. For the most part, they are played evenly, but in a lot of funk music, the last sixteenth note of a beat has a little swing, or accent, to it. It appears that most of the notes in this solo are tongued. In bars 13-15, Trombone Shorty uses a double-tonguing technique, with an added glissando, to multiply the rhythm from 16th to 32nd notes to growl, or flutter-tongue. He even tops that in bar 28 with the sextuplets on a G major triad. It appears that each note is articulated with the use of triple-tonguing.
And also notice the phrasing used in this solo. While most of the phrases are only a couple beats in length, when strung together logically, they build larger 4-bar and 8-bar phrases. There's even a nice arch to the entire 32 bar solo, where all these little ideas build up to bar 17, the climax, and then come back down with a flourish. Think of it as words that are strung together to formulate a sentence.
If the sextuplets are the exclamation point of this sentence, then the main subject must be the powerful high B natural. I don't know how to even practice getting that quality of tone and the sheer force behind it, but Shorty builds up tension and anticipation through use of crazy rhythm and a growling tone. To contrast this, the high B is held out for a long duration and his tone is absolutely glorious. He plays it going into the start of the new phrase and surprises you early with it, whereas you would expect it to fall on the downbeat of the bar 17. The pleasure comes in bar 16 when you realize that you have already arrived. This is commonly referred to as hitting "The Note."
For a better understanding of "The Note," listen to guitar players like Jimi Hendrix or B.B. King. Clearly, Trombone Shorty has been influenced by the guitar. This solo, and many of his other solos, are built around a minor pentatonic scale similarly to rock guitar solos. This solo uses the E minor pentatonic which is also the basis for how a guitar is tuned. He uses pentatonics so much that he actually confused me in bar 21 by playing a simple E minor scale. I had forgotten what this pattern sounded like and it became one of the hardest patterns in this solo for me to hear. So, don't forget to practice your scales. When you run out of ideas, or have used up all your other patterns, you can always fall back on your scales.
SPECIAL THANKS to Andrew Mitchell for providing some insight:
One of the Artists-in-residence at my University who had the privilege to play next to Trombone Shorty said playing next to him while he played his growl "sounded like a damn machine gun. I have no idea what he did or how he did it, but man was it exceptional!"
Because I couldn't find a live video of this song, here's the YouTube video that introduces you to Trombone Shorty.
Recommend Reading: Thirty-Six Studies For The Trombone with F Attachment, by O. Blume. Arranged and Edited by Reginald H. Fink. Published by Carl Fischer.