Sandman/Dick:
"the advantage of duet concertina for blues is that it can use piano blues techniques for a model".

What "piano blues techniques" do you refer to? Can you give some examples? The three available tune samples on your website sadly don't include some blues.Since the accidentals on an English are located directly beside the major scale notes it might seem pretty handy to make the similar kind of slides on the English like Bb/B or Eb/E as with the piano but as you actually can't really slide with the finger as on a piano keyboard I think it hardly matters for that particulr issue what kind of concertina keyboard is used. For walking bass or boogiewoogie piano style I have the impression that the choice of key may be more important than the choice of concertina type
Concerning *vibrato* and *tremolo* there are some common nomenclature problems but most often in encyclopedias and acoustic textbooks *vibrato* is a variation of pitch and *tremolo* a variation of amplitude. Thus with concertina ( and any squeezebox) shaking the bellows better be called a *tremolo* while a *vibrato* in that sence is impossible to achieve with a free reed.

gillymor,
Concerning "Rhythmic bounce" with an English the challenge lies firstly in bellows control - when playing energetically !- and THIS normally is much easier to do with the Anglo/Duet kind of handle than the traditional English thumbstrap and finger rest. IF wanting to play EC with much rhythmic energy the handle may be reformed to become more stable by adding a wide wrist support, a wide steady wrist strap and more stable thumbstraps than the trad ones.