The conventional ideal of glassy smoothness in everything I find spurious to my purpose, with rough figures being far more productive of good ideas owing to the unintentional accents within them.
Well, I apologize for continuing to get a bit OT, but I find this interesting in that this is my basic approach to many things in classical repertoire, and in jazz.
I don't
want "smooth, pearly" scales, many times.
In Bach, I want phrasing for melodic lines, sometimes with pronounced points of articulation depending on the character of the piece, and different articulations for arpeggiated figures.
In bebop, I like to attack the scalar lines (alas, still mostly done in RH, despite my efforts to do more work on octaves and tenths splits between both hands, like Bill Evans was doing in his later, more free-form interludes later in his career, or so many others) — it's just, IMHO, many ways the music should sound, at least as I like it.
Of course, one needs both options, especially for classical repertoire — the smooth and the rough — but by all means smooth, even, glassy scales is just one option.
So, if you improvise, and it's not classical, and it's not jazz (I'll include all the subsets of popular music under that umbrella, as is my wont), do you have a link? I'm curious what that might sound like.
ETA back to the OP and many-keys work: I wonder if it occurred to him or her to ear-tranpose the Bach two-part inventions (or some of his other simpler pieces) into the other keys?
I have never gotten around to that, personally, but I'd have to think the benefits for learning more about music theory, as well as the many spots in such pieces where isolation-work on five-finger motifs (the C major, pretty much could be adapted into a Hanon-esque exercise by extraction) or the Bb (isolated work on fingers 3-4-5 in LH), as well as the rest.
I'd sure be doing that if I wanted to do some real woodshedding — although I suppose it would be far easier to just man-handle the Hanon bits into whatever key desired, because of their brevity and lack of musical content.
EETA And, yes, I know mostly this is a classical board. It's just — and here, I would think most people would benefit from this — that I prefer to think of the piano as an abstraction, abstracted away from any specific repertoire. I mean, really, it's a box of metal and wood, and the techniques needed to make it sound good aren't so different no matter what the style.