I try to minimise what John Vernon described as "Anglo player's shake", i.e. lots of bellows reversals, by using alternative buttons. There is much more scope for this on a 40-key (or, I suppose, on a Jeffries 38-key, of which I have no experience) than on a 30-key. I do this partly for more legato and partly out of simple cussedness. People who see me play sometimes think I am playing a Duet. I should mention that I regard this as a matter of personal preference, not a matter of right and wrong.