Listen to the 1st Estudos: https://youtu.be/yFG-X2vyZsM
The 12 Estudos were written in Paris in 1929 and are dedicated to the famous guitar player Andrès Segovia. Although these studies are of technical interest, they still have musicality.
The first 3 ones deal with the arpeggios playing. Also note that in these 3 studies each measures is repeated 2 times.
The first study has no theme or melody, but uses arpeggios over chords changes in the E minor key in the same way as in the first J-S Bach prelude of the Well-Tempered Keyboard. The right hand plays the same strings (with the same fingerings) for the arpeggio all along the piece, except in the last 2 measures (since there are plated chords) and during the climax (the approach notes in measures 24 and 25).
This study could be divided in 3 parts and a coda (ABA’ form).
From measures 1 to 11, the bass line follows a stepwise upward motion from the tonic E to the dominant B. Moreover the register is going upward to. This may suggest a crescendo for the interpretation.
From measures 12 to 23, passing diminished chords are played over a tonic pedal bass. They follow a chromatic downward movement and certainly suggest a decrescendo. This process is characteristic of the Villa-Lobos guitar music. We find it back in the concerto and in the 5 Preludes.
From measures 24 to 29, there is a climax because here is the most treble tone (E, the tonic). Moreover, this time the arpeggio of the E minor chord is played on 2 octaves (measure 24) and is replaced by approach tones in measure 25. So measures 24-25 could be played forte subito.
From measures 30 to 34, this is the coda. After the concluding V and I chords (measures 29 and 30), we find back the E minor arpeggio of the first measure.
Interesting or curious chords progressions and combinations of notes:
Measure 1-2: it is the same progression as in the 1st Prelude of the Well-Tempered Keyboard (I and II over a tonic bass) except that here it is written in a minor key. The tonic is a pedal and the arpeggios follow a stepwise motion.
Measure 10: there is a delayed 4th.
Measure 12: note the avoided resolution of the dominant chord to the E7b9 chord (G#°7/E).
Measures 8 and 27: note the use of 11th tensions on -7b5 chords. In measure 8, the E-7b5 chord could be understood as a C7 chord (a substitute of the V/V) since there is a 4th and 6th inversion of the I chord in measure 9 (and finally a dominant chord).
Measures 26 and 27: The V7 to II-7b5 chord progression (instead of first II and then V).
Measures 33 and 34: the final IV-7 to IM6 chord progression recalls baroque codas, but Villa-Lobos modernized it with the m7 and the M6.