Foolestroupe:"I can usually get stronger emphasis on the "pull" than the "push"... and by 'twisting' or pulling the bellows not straight out, but 'swivelling' in the vertical plane, you get a higher leverage, and thus more 'punch' on the pull than you can get on the 'push'... if some 'expert' tells you than you should not play that way, just smile, nod, say 'yes dear' and ignore them... "

RE: Thanks, I clap my hands ! I have been saying this to concertina players for years - telling them that "any accordion player" knows: a) what bellows work means for expression b)that by "twisting" - as you say - or "fanning" as I use to call it - you can achieve better control, and "punch" as is said here. I guess you agree that this is also an essence in the "bellows shake" which maybe can not be exactly simulated with concertinas but many other ways to produce "tremolo" can be practised to get similar effects.