This is a great falseta which showcases some interesting things in the harmony as well as in the rhythm. One thing to look for right away is his treatment of the II chord. He goes between major and minor quite a bit which gives a very unique quality. Let's take a closer look:
Measure 1: Starting on the Bb7 chord, he quickly changes it to a minor 7th to serve as a nice chord melody change back to the A.
Measure 5-6: Take a look at how Jose goes to the borrowed E chord in measure 6. In measure 5 he starts with a D minor in first inversion over F (Dm/F), to C/E, then to an F chord which sets up this change to the E chord beautifully.
Measure 7: After borrowing the E chord in the previous measure from our parallel major/harmonic minor keys, he goes right back to the A(b9) type of chord which many of you are probably familiar with but then goes to a Gmin7/Ab which is also fairly common taking the vii chord ad adding a b9 in the bass. That type of chord usually takes you right back to A not here.
Measure 8: This chord is probably one of the hippest substitutions I've come across. Talk about surprise chords this one takes to cake. It is a Dbmaj7/Ab functioning as a minor ii chord in disguise. The notes it shares with the II chord are the C natural which would be the 9th of a Bb, the F which is the 5th of the Bb, the Db note would be the minor 3rd of a Bb, and the Ab in the bass would be the minor 7th of the Bb. This shows you how much substitution can take place on the II chord with a little bit of creative thought.
Measure 10: Here Jose is repeating the beginning of the falseta but then adds a second ending with a quick F7 - E7 change before the next measure.
Measure 11: Note how we have the D and the G# which are the 7th and 3rd of the E7 and how the spelling changes when he goes into the next chord. Those two notes are now part of the Bb7 chord but one is enharmonically spelled as an Ab which is the dominant 7th of the Bb chord. This is a perfect example of how he goes back and forth from two dominant type chord that serve the I chord. E7 and Bb are essentially interchangeable as a flat V substitution.
Measure 12: This measure is essentially a Bb7 harmony but from the shape of it alone it makes you see the interconnectedness of the Gminor chord (vii) and the Bb (II). Remember that chords that are a 3rd away from each other share many notes as well as function.
Measure 13-14: Here Jose ends the picado run back to A and then gives a nice rhythmic punch at the Bb and A chord. He then in measure 14 leads you back to the E7(b9) which is an outside chord getting quite a bit of treatment in this falseta.
Measure 15-16: Here's that E7 to Bb/F change that leads us back to A.
Measure 21: Here we have a G7 chord which is a borrowed dominant for the C (III) chord.
Measure 22: This is a great ending in where Jose uses the thumb and index to create a offbeat melody to add tension and then finally resolve back to A.