Schübler Chorales (BWV 645-50)
Introduction
The Schübler Chorales belong to a small handful of works printed and published during Bach’s lifetime. In 1747, late in the composer’s life, Bach assembled a new set of six chorales in which five of the six (Nos. 1, 3, 4, 5, 6) were transcribed to organ from movements selected from five previously composed cantatas, published in 1748 by Johann Georg Schübler (ca. 1720-1755). All chorales except one, from BWV 6, are literal transcriptions with the number of measures and original tempo being unaffected. The five cantatas originate from the years 1724, 1725, and 1731 – showing a gap of 23 years from when Bach decided to assemble his new set of chorales plus newly composing Chorale No. 2.
Study of the organization of the six Schübler Chorales indicates that Bach either had a superior memory that retained detailed information for at least 23 years and/or Bach had a special system of filing and organizing his 200-something cantatas, of which only one was published during his lifetime, BWV 71. Otherwise, it would have been impossible to organize the six chorales into three neat duration pairs, in which the first and sixth chorales relate 1:1, the second and third chorales relate 1:2, and the fourth and fifth chorales relate 1:1 within a mere 0.5% average margin of error:
To understand Bach’s thought process in assembling the six Schübler Chorales, it is first necessary to analyze the five cantatas from 1724, 1725, and 1731 – Nos. 140, 93, 10, 6, 137 – which may be studied in the “Selected Cantatas” chapter. After these five cantatas are closely studied and all the duration ratios are uncovered, understanding Bach’s intentions in the Schübler Chorales becomes straightforward and totally logical.
Step 1 – Secure the Bookends
To begin, Bach selected the third movement from Cantata No. 140, tenor chorale, and the second movement from Cantata No. 137, alto aria, which have virtually equal durations of a little over four minutes each. These two movements, originally composed in 1731 and 1725, share accurate duration ratios with neighboring movements – a 3:2 duration of 6:18-4:12 and a 1:1 duration ratio of 4:00-4:00:
Bach then placed these two organ transcriptions, BWV 645 and 650, at the beginning and end of the opus to provide the bookends or The Alpha & The Omega (see Chapter 4). It is significant that with durations of just over four minutes these two chorales are the longest of all six, which provides a strong first-last foundation for the opus. These first and last chorales have equal durations because the beat ratio and tempo ratio both reduce to 3:2, 296:198 and 72:48, resulting in equal durations (3:2 beat ratio ÷ 3:2 tempo ratio = 1:1 duration ratio):
Step 2 – Establish Relationship between Chorales 2 and 3
Next, after securing the bookends to the opus, Bach selected for the next transcription the fourth movement from Cantata No. 93, soprano-alto duet. This movement, originally composed in 1724, has a duration, 3:10, virtually equal to that of the third movement, 3:06, or, both durations of a little over three minutes:
Bach used this transcription as the third movement of six, in which he next added a newly composed second movement not borrowed from a cantata. The newly composed chorale has a duration virtually half of 3:10, showing that Bach planned a 1:2 duration ratio here, 1:35-3:10. Bach achieved this by making the beat ratio, 132:200 = 2:3, half the tempo ratio, 84:63 = 4:3, resulting in a 1:2 duration ratio (2:3 beat ratio ÷ 4:3 tempo ratio = 1:2 duration ratio):
Step 3 – Establish Relationship between Chorales 4 and 5
Finally, Bach selected for the last pair the fifth movement from Cantata No. 10, alto-tenor duet, and the third movement from Cantata No. 6, soprano chorale. These movements, originally composed in 1724 and 1725, have unrelated durations of 2:30 and 4:10, although in context of the original cantatas, each shares a 1:1 duration ratio with its neighboring movement:
Bach rectified the discrepancy of unrelated durations, 2:30 and 4:10, by omitting the repeat in the latter – more specifically, the third movement of Cantata No. 6 consists of 100 measures of 4/4 while the fifth chorale, otherwise identical to its cantata model, consists of 41 fewer measures, 59, resulting in 1:42 less time. It is quite astonishing that Bach cut out the precise amount of time (via measure subtraction) to achieve the same two-and-half-minute duration as the fourth chorale: 4:10 – 1:42 = 2:30. Bach achieved this by making the beat ratio, 132:200 = 2:3, half the tempo ratio, 84:63 = 4:3, resulting in a 1:2 duration ratio, 1:35-3:10 (2:3 beat ratio ÷ 4:3 tempo ratio = 1:2 duration ratio):
