Further to Bayan time: a progress report about the Орфей six weeks on (I thought I'd document it, on the vague possibility that it might help anyone else learning the bayan (B system chromatic button accordion).
It's going extremely well, considering the radical difference from a piano keyboard system and that I'm largely on my own. It took about a month of solid practice to get reasonably comfortable with the unfamiliar note locations (left). The bass - left hand - proved more of a problem than I expected; although it has the same Stradella system as the piano accordion I'm used to, the buttons are considerably closer in spacing, and I'm still finding them a rather cramped. Actually, it's not quite the same system as I'm used to; being a full 120-bass, there are the counterbasses and extra chord rows to learn (as well as unlearning some of the ways of making chords unavailable as presets on the 24-bass).
However, I'll put a demo on YouTube shortly; I can already play some of my party pieces from the piano accordion (Stormy Weather, and the ubiquitous Bluebell Polka). The chromatic layout is proving very versatile, equally comfortable for simple Morris tunes and heavily chromatic tunes like the Pink Panther theme. I highly recommend the bayan for its tone; the eBay description called it "a strong sweet voice" but I wasn't prepared for how different it would be. The default reeds have a powerful and mellow clarinet-like flavour quite unlike the stereotypical accordion, but it has four other voices including a "wet" tuning giving the classic French musette accordion sound.
The single most useful website I've found so far has been Blumberg's Music Theory Cipher, which has helpful charts of notes, scales, triad shapes, and general note relationships within the chromatic keyboard. And the second: YouTube. Once you get past the depressing bits - such as the virtuosity of Lidia Kaminska and Alexander Dmitriev - it's seriously helpful in showing things like hand position and which fingers to use (there's an interesting interview with Lidia Kaminska on the technology and technique of bayan playing here). But for clear examples of more achievable playing, I've found the Bayanina Music channel especially helpful.
Looking at YouTube and website discussions, there doesn't seem to be much consensus over use of the thumb: some players brace it against the keyboard edge and just use four fingers (it seems to have been standard technique in the past); some use it to play. Personally I go for the latter, as my little finger doesn't work very well. A second area where opinion seems to vary is whether to stick to three rows (the darker grey section in the image above). Some do, and it has the advantage that you can learn the pattern for a single scale, and play in any key by shifting that pattern elsewhere on the keyboard. However, looking on YouTube at what players actually suggests this shouldn't be stuck to obsessively, or even at all: in context, often notes outside the three-row scale make a better alternate fingering.
I've one major warning: watch the shoulder and back. A heavy accordion (and the Orfei weighs 10kg) is working the rotator cuff of the left shoulder especially hard. I've found it most comfortable to play sitting, and use the left thigh to support the left half of the bayan and do some of the effort of working the bellows.