Interesting… maybe it's a national peculiarity then. In Hungary, almost everyone calls this kind of articulation a "minuet step". Go figure.

@Patrx2 (By the way, the sheet I'm writing is probably going to be used by a semi-professional choir, so there's no need to superficially ease readability by not using double flats.)

@Patrx2 "My point was that different contexts might lead to different choices" – exactly. That's the main reason I've asked this question :)

@Patrx2 Actually, I ended up following your more rigorous advice, and I've written C♭ and E♭♭.

Yes, it's in A minor. Just check the beginning and the end of the piece. It's very obvious that it's in A minor. The fact that there are other notes does not change the key. It's not even a tonal excursion, let alone modulation. (In fact, it's very common to use the sharp fourth in minor keys. It's a good tool to make certain parts sound more "exciting", so to say.)

I'm sorry, I may have been misleading with the wording. I am playing this on the piano. I've also found the PDF you linked to, and the original cadenza is not what Cziffra plays. If you listen to it, you will hear that the last part of the last bar is not a simple scale, but it goes up, down, up, down, and then up again.