Micro study 6 is the rest of bar 14, where Villa-Lobos has opted for a new harmonic device, the cycle of V. Using only 2 chord shapes, a major shape built off a 6 string root and a dominant 7 shape built off a 5 string root, the music descends the fretboard in a whole tone fragment again: bass C# B A G F; melody the same.
The chords outline a cadence sequence, F#7 (V) to B (I), E7 (V) to A (I) and so on, but starting from C#.
Main points here are: