I've been learning what I think it possibly the hardest piece of Bach I have tackled to date. I'm not trying to be pretentious by putting my rather poor efforts in here, but highlight a few of the differences between the genuine virtuoso and the run-of-the-mill grade 8 or so pianist who will never get any better.
The piece in question is the prelude number 3 from Book One of the Well Tempered Clavier. Bach placed these pieces in order of key: C major, C minor, C# major, C# minor, D major, D minor etc. up to number 24, in B minor. He wrote the first 24 (Book 1) in the early 1720s when he was at Anhalt-Cothen, and Book 2 in about 1737 when he was in Leipzig. Neither work was published until 1801, 51 years after Bach's death. No-one knows for sure exactly why he wrote them, and it certainly wasn't for a big powerful instrument like a modern piano. None of them has a range greater than 4 octaves, which implies a clavichord, and therefore domestic music with only a few, if any, listeners apart from the performer and, possibly, a teacher.
The first question has to be, in the piece in question, why did he choose C# as the key? The notes are exactly the same as for D flat major, but C# has 7 sharps in its key signature, whereas D flat has 5 flats. The result of all these sharps is that every note in the home key, white or black, is a sharp, so if he wants to change key at any point, and of course he does, you end up playing a whole sequence of double sharps. This, for the performer, means that you are playing a note written on the stave as, for example, an F of some description, but you are pressing the key you normally associate with being a G. As you can imagine, this really "does yer 'ed in" when you are first learning the notes.
My weaknesses as a pianist are several: I think my worst is inconsistency. In any piece, some passages are harder than others, and to master them you have to practice repeatedly and slowly. Gradually, as you ingrain the right notes into your hands and brain, you can speed up . This I can do, but I have a dreadfully annoying habit of not paying sufficient attention and I'm always liable to make a silly mistake through inattention. I don't know how to tackle this. It's the reason I'll never perform in public: I can't ever guarantee that I'll be able to get through a piece without some sort of serious error. Curiously, I've been far less nervous when playing for exams than I have on the few occasions I have played in public.
I've recorded myself twice, warts and all, once rather slower than the piece is meant to be played, and even in that I've made a couple of slips, and the second time, up to speed. I'll also link to Angela Hewitt, who has recorded this piece on her own beautiful Fazioli during lockdown. Angela is a top-notch international pianist and a Bach specialist.
My first take (sedate):
https://www.youtube.com/watch?v=8GXsn8Zf6wA&ab_channel=PeterWalkerSecond take:
https://www.youtube.com/watch?v=oGO5cBvK4uU&ab_channel=PeterWalkerAngela Hewitt:
https://www.youtube.com/watch?v=J_o3gMO5iqw&ab_channel=NatalieSchwamovaI would be very interested to find out how much time a great pianist like Ms. Hewitt has to spend on a piece like this to get it up to that standard. My guess is "Not a lot". I've not logged how long I've spent on it but I shouldn't think that it has been less than 2 hours on any day in about the past 10 days to a fortnight, and I've played pretty well nothing else. I'm going to tackle the fugue next, and that has precisely the same difficulty regarding the number of sharps, and is also about twice as long. It puts into perspective the enormity of the performance of Andras Schiff when he played the whole of Book 1 (about 2 hours' music) at a single sitting in the Proms in 2017. Having that much music memorised and concert-ready at once is, to me, absolutely mind-blowing.