Agua De Beber

The second bar gives the problem away: two altered dominants in a row, in the same bar, heading for the same place. That figure repeats through the whole tune.

Eighty-six chords, forty-six of them dominants, thirty-two admitting more than one reading. When two chords share a bar the rule changes: it isn't always two scales. Knowing when it's one is what separates a line that flows from one that stumbles.