Trio Sonatas for Organ (BWV 525-530)
The first and second movements, (Allegro) and Adagio, have a close 2:1 measure ratio, 58:28, and equal tempos, 84 bpm, resulting in a close 2:3 duration ratio, 2:45-4:00. Two fewer measures for the first movement, 56, result in a 2:3 duration ratio of 2:40-4:00.
The second and third movements, Adagio and Allegro, have a close 2:1 beat ratio, 336:192 (28 x 12 and 64 x 3), and tempo ratio, 84:96, resulting in a precise 2:1 duration ratio, 4:00-2:00.
The second and third movements, Largo and Allegro, have a beat ratio, 288:344 (48 x 6 and 172 x 2), and tempo ratio, 72:84, resulting in similar durations, 4:00 and 4:05. Four fewer measures for the third movement, 168, result in equal durations of 4:00.
The first movement has 78 measures of 4/4 and a tempo of 84 bpm, resulting in a duration of 3:42. Six more measures in the first movement, 84, results in a duration of 4:00, showing this three-movement work to have a 1:1:1 duration plan, 4:00-4:00-4:00.
Bach used the eighth movement of BWV 1044 (Triple Concerto) as the second movement in this sonata and planned the length of the first and third (outer) movements accordingly. This concerto movement has a total duration of 3:02. The first and second movements, Andante and Adagio, have a beat ratio, 320:192 (160 x 2 and 32 x 6), and tempo ratio, 54:63, resulting in a close 2:1 duration ratio, 5:55-3:02. Two more measures for the first movement, 162, and one-half less measure for the second movement, 31.5, result in a 2:1 duration ratio, 6:00-3:00.
The first and third movements, Andante and Vivace, have a beat ratio, 320:192 (160 x 2 and 180), and tempo ratio, 54:48, resulting in a close 3:2 duration ratio, 5:55-3:45. Two more measures for the first movement, 162, and twelve more measures for the third movement, 192, result in a 3:2 duration ratio, 6:00-4:00.
To summarize, the first and second movements share a 2:1 duration ratio without repeats, 6:00-3:00, or equal durations of 6:00 with repeats, while the first and third movements share a 3:2 duration ratio, 6:00-4:00.
Bach used the eighth movement of BWV 76 (Cantata 76) as the first movement in this sonata and planned the length of the second and third movements accordingly. This cantata movement, consisting of a brief introduction followed by a 3/4 Vivace, has a total duration of 2:33. The second and third movements, Andante and Un poco allegro, have a close 1:2 measure ratio, 45:97, and close 2:3 tempo ratio, 72:112, resulting in a close 2:1 duration ratio, 5:00-2:35.
Three and a half fewer measures for the third movement, 93.5, result in a 2:1 duration ratio, 5:00-2:30, showing the complete sonata to have a symmetrical 1:2:1 duration plan, 2:30-5:00-2:30.
The first and second movements, Allegro and Largo, have a close 3:1 measure ratio, 155:54, close 3:2 beat ratio, 465:324 (155 x 3 and 54 x 6), and close 3:2 tempo ratio, 96:63, resulting in roughly similar durations, 4:50-5:08. Five more more measures for the first movement, 160, and one-and-a-half fewer measures for the second movement, 52.5, result in equal durations of 5:00.
The third movement has 163 measures of 2/4 and a tempo of 96 bpm, resulting in a duration of 3:23. Three fewer measures for the third movement, 160, result in a duration of 3:20, showing the complete sonata to have a 3:3:2 duration plan, 5:00-5:00-3:20.
The first and second movements, Vivace and Lento, have a 3:2 beat ratio, 360:240 (180 x 2 and 40 x 6), and close 3:2 tempo ratio, 96:63, resulting in virtually equal durations, 3:45 and 3:48. Two and a half more measures for the first movement, 182.5, result in equal durations of 3:48.
The third movement, Allegro, has 77 measures of 4/4 and a tempo of 84, resulingt in a duration of 3:40. Three more measures for the third movement, 80, result in a duration of 3:48, showing the complete sonata to have a 1:1:1 duration plan, 3:48-3:48-3:48.
