Di Sarli recorded El Choclo in 1954. His interpretation is lush, with beautiful , skillfully contrasting bandoenons and strings. And the piano, played by Di Sarli, has the melody in Section C, bar 49. Di Sarli’s interpretation sharply contrasts D’Arienzo’s. It is much slower and has a softness, a lyrical character overall, compared to D’Arienzo’s very rhythmic and fast playing.
The form Di Sarli uses is A-B-A-C-A. This particular is called rondo in music theory. An initial (A) is heard then a different one (B), followed by a restatement of the first (A), then another different one (C). In rondo form there must be at least two different sections, the first section must be played between them, and the first section (A) must also be the last one. Di Sarli shows his skill and musical knowledge here. The return to familiarity from contrast and the new is part of the charm and purpose in rondo form. Di Sarli was a consummate musician.
Orchestration or instrumentation is how the instruments are used; which instruments are playing at any given time and what is their function, such as melodic, accompaniment, creating the pulse, linking phrases (fills).
Marcato is Italian for marked, meaning the notes are to be accented and emphasized. In tango the notes are also played clipped or cut shorter than the note value as written. That is called staccato. The performance style, the articulation, combines marcato and staccato. And that gives the music a crisp and bold character. When I use the term marcato those are the qualities I mean.
Tango uses marcato style playing very often, especially in the accompanying instruments, frequently the bandoneons but others as well.
Music that is smooth and connected, with a flowing character, often with a broad sweeping melody and gentle accompaniment.
Composers/arrangers make a very conscious decision regarding form. The order sections are heard greatly effects our sensations and responses as listeners and dancers.
Sections are the top level element of music's form. They are the the large building blocks of tango music, typically lasting around thirty seconds or so. Each section is a unique segment of music, having a distinct musical character.
Tango music has two, occasionally three, primary sections, which we may label “A”, “B”, “C”. Sometimes there is an "Introduction", "Bridge", a short section between two larger ones, or "Coda", a short concluding section.
Usually each section will be played consecutively in order (A then B then C), followed by various other orderings. Typically in tango songs each section is played instrumentally then each is sung, then section A is played instrumentally: A-B-A (vocal)-B (vocal)-A. But there are many exceptions and other possibilities.
Phrases exist within a section.