In Day 3, we will learn measures 6-7 of the chorale prelude "Liebster Jesu, wir sind hier", BWV 731 by Bach on the organ. But before you do that, I strongly advice to repeat previously learned material from Day 1 and Day 2. If you can do this without making too many mistakes in a slow tempo, then it is OK to play all four parts combined right away.
If not, go back one or more steps in your practice and play combinations of 3 voices, 2 voices, or even solo voices - S, A, T, and B. Whatever the case is, always practice until you can play each fragment correctly at least 3 times in a row correctly. NOTE: if you make a mistake in the second repetition, you will have to start counting from the beginning again.
In measures 6-7, the pedal line moves in constant eighth notes and if you can play it with the alternating toe pedaling (using the toes of the same foot only in places where the melody changes direction), you will begin to notice a gentle alternation of strong and weak beats.
Remember that in this meter (4/4), there are 2 stronger beats (1 and 3) and beats 2 and 4 are weak. It is especially difficult to feel this pulse and alternation while playing in a slow tempo. Therefore I recommend to count out loud the beats and their subdivisions. Then you will be conscious of the pulse and your playing will be stylistically correct.
This brings me to another important aspect - articulation. Aim to achieve small spaces between each and every note in this fragment. Try to do this even when you will play two voices (alto and tenor) with the left hand. This touch should not sound choppy or too detached. Instead aim for a singing manner of playing (Cantabile).
The mordent in the left hand part (measure 7) should be played on the beat starting from the upper note (E D# E D#).
Before you start practicing various voice combinations, figure out the fingering of this fragment without using finger substitution. Play with 3 longer fingers (2, 3, and 4) as much as possible, and use shorter fingers (1 and 5) only when necessary.
Apply the following steps when practicing this fragment for Day 3:
Step 1: Practice solo voices separately (S, A, T, B).
Step 2: Practice 6 combinations of two voices (SA, ST, SB, AT, AB, TB).
Step 3: Practice 4 combinations of three voices (SAT, SAB, STB, ATB).
Step 4: Practice all four parts together (SATB).
Enjoy your practice and insist on at least 3 correct repetitions in a row of each combination. This way your progress while playing this fantastic piece on the organ will be the fastest.
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Or if you want to learn to improvise in the style of Bach? If so, I suggest you check out my free 9 day mini course in Keyboard Prelude Improvisation.