Dick/Sandman, I absolutely agree concerning reversals and Anglo playing that the common difference between *most* anglo playing and *most* english playing is just THAT : When playing anglo you spontaneously get more rhythmical feeling since you HAVE to reverse bellows a lot more often. Being lazy and playing english you just pull the bellows out till it stops and push it in again until it stops. Often people forget articulation of tone and phrases completely on the route...
Jack Campin, Bellows shake mostly is trickier with concertinas than with accordions since you seldom got the same stability holding the concertina between your hands and the bellows itself being 6,8, or 12 sided instead of 4-sided makes it much floppier.The technique with an accordion is keeping the lower part of the bellows closed and doing the reversals only with the top end of the bellows. There are some accordion players who facilitate this by keeping the lower bellows lock/strap closed to increase stability even more. I use that trick myself almost all the time by having elastic "cross-the-bellows-straps" to stabilize the bellows work and this makes almost all playing a lot easier since pumping is more effective and articulation of tone very much more accurate. I made some YT clips myself many years ago trying do illustrate it: