When J.S. Bach first got to know the music of Venetian maestro Antonio Vivaldi during the early 1710s or perhaps just a bit earlier, he was significantly impressed by his Italian colleague's flair and style, and skill. Young Duke Johann Ernst of Saxe-Weimar, the nephew of Bach's employer at the time, happened to have a taste for Italian instrumental music, so Bach took it upon himself to adapt several Italian (or Italianate) instrumental concertos -- mostly by Vivaldi, but some from Marcello, and even a bit of young Johann Ernst's own music -- for performance on harpsichord alone (there is also a corresponding and contemporaneous set of such adaptations for solo organ: BWV 592-597). In so doing he both pleased the Duke and began to absorb elements of the new Italian style into his own music-making. The first of the Vivaldi concerto transcriptions is the Concerto for keyboard No. 1 in D major, BWV 972, modeled upon Vivaldi's Concerto for four violins and continuo, Op. 3, No. 9 (RV230).
Like its source, BWV 972 is in three movements, fast-slow-fast. The first movement, which has no tempo indication but which would have immediately been recognized by contemporary players as an allegro, begins with a handful of separate aristocratic gestures and then gains momentum and spins out continuously until its end. Bach does more than just take the notes of Vivaldi's concerto and condense them onto two staves for one player to play; he thickens the textures considerably (Vivaldi loved lean music, while Bach usually loved full, rich, dense music), adding bits and fleshing out counterpoint along the way. The following Largo (Larghetto in the Vivaldi, and also in some editions of the Bach) pulses with warm eighth notes from start to finish. The tuttis are made from these "simple," homophonic tones, but in the solo passages smaller and more flexible lines are drawn in and around this pulsation. The third movement is a dance-like 3/8 time Allegro that begins with a duet in parallel thirds, and which Bach supplements with several passages of his own, passages not found in the Vivaldi at all.