A more detailed analysis will soon follow. WARNING!!!(Score has a slightly more virtuosic version than video and will be updated soon) BB
The falseta starts in the mode of F Lydian (F major scale w a #11), goes to Amin9 then repeat.
The Amin9 goes to a Gmin/Bbmaj harmony then repeat.
Then the cool twist is when it goes to "por Granaina" or B altered Phrygian.
The B(b9) chord then acts as the V chord of E minor and resolves.
Then we switch back to F Lydian then repeat.
Finally the Remate uses Fmaj(#11), Gmaj(#5), Fmaj(#5) then resolves to E(b9)add11 (por Arriba).
*********(An extra tip... try replacing the last chord - E(b9)add11 to an A(#5)/G to go to "por Medio". This Falseta can be played "por Arriba" or "por Medio" depending on where you want to go. Happy modulating everyone!