In the time of Vivaldi there were four types of concertos: the solo concerto (for which we best know him), the concerto grosso for more than one instrument and strings, the chamber concerto for few instruments, and the string orchestra concerto (often titled Sinfonia). The Concerto in C is of the last type, of which Vivaldi composed 60. Predictably, the two violin sections receive the lion’s share of attention.
The ritornello of the opening movement is a bright C-major theme in several sub-themes (or motives). Then, between statements of sub-themes, the violins play energetic, perpetual-motion material at first, but later, more relax rhythms. At nearly the halfway point comes an unexpected pause, followed by a sudden shift to C minor! Snippets from the ritornello theme are transformed and worked out like a small symphonic development. Then, just as suddenly, Vivaldi lands us back in C major for a reprise of the ritornello, which concludes the movement.
C minor returns as the principal key of the Andante. Essentially, this is a graceful minuet. Again, the composer features a tight-knit grouping of the two violin sections, now supported simply by chords in the lower strings.
Italian Baroque finales were traditionally dancelike and in a bright triple time. This C major Allegro finale follows suit. Also traditional is its two-part form with each half repeated. Here, the melody is so simple that the section repetitions seem to invite melodic ornamentation or other variants. Held out notes in the second section are especially inviting, particularly since they lead to a big upward sweep in the violins that concludes the finale.