I’ve developed a daily warm-up method; it’s not long, maybe 15 or 20 minutes. I believe it’s an important process. I’m not sure what other players do, though I am curious. Ton Koopman uses 4 Cramer studies, and those are very good indeed. Mine are very simple, deceptively so. They serve to relax the fingers, arms and body, connect the fingers, ears and brain, and focus mostly on small non-simultaneous plucks as well as exactly when the note is released/damped.
I begin with do-re-mi-re-do, back and forth in parallel 6ths maybe 4 times, starting on c below middle c in the left hand, the right hand on a. Using only fingers 2, 3 and 4. All notes held down, only raised to repeat that note when it comes around again. Then working up the degrees of the C major scale. Same thing, next on the D major scale; Eb, E, F, G, A and then Bb major. Kind of like a meditation, become aware of how relaxed the arms and hands are, how well you’re sitting, the quality of the sound. Be aware of tiny non horizontal plucks between the hands, and vary them. Notice where your wrists are, how curved or horizontal your fingers are, how close the keys they stay. I found this exercise improves the ease and quality of trills immensely.
The next one is similar, but you only over-hold two notes at at time. The pattern is do-re-mi-do, re-mi-fa-re, mi-fa-sol-mi, et cetera. Starting with the C major scale, again in parallel sixths, going on to the other scales as in exercise 1. Notice how the left hand plucks just a little bit ahead of the right, then switch them. The key is releasing do just when you pluck mi, and when you release mi you release re at the same time. Koopman showed me this one, and it’s very helpful for achieving precision in the timing of note releases, as well as making 2-note over-holding an easy instinctive thing. I do this one up the scale, and then in reverse down the scale.
My third pattern is an ascending up the scale and then descending triplet pattern: do-re-mi, re-mi-fa, mi-fa-sol, et cetera, with the three notes overheld. Fairly quickly, but never faster than you can control the non horizontal plucking, and never so fast that you lose the suppleness and total relaxation of the hand and arms. Then, I start over again, but with the left hand staccato (the fingers scooping inward) while the right hand is completely overlegato, and then reversed (the right hand staccato and the left over legato), and then both hands staccato. All the time, maintaining awareness of how subtly separated the plucks are between the two hands.
Finally I progress to using all four fingers (not the thumb though), the pattern in C major being do-re-mi-fa, re-mi-fa-sol, et cetera ; rising an octave and then descending back to your starting point. Both hands overlegato, then the right over legato while the left is staccato, then reversed. This one I just do in C major, because I think that’s just enough, most days.
Of course this isn’t a comprehensive method, it’s just a brief warmup. Yes, a few arpeggios are sometimes helpful to add. But the point of this is to connect the brain, ear and fingers to the fine details of over holding and non simultaneous plucking before diving into the day’s music and it seems to be very effective for that.