Wheastone's 'Mayfair' range used accordion reeds, and sounded like it! It was an attempt to boost sales, but they were cheap and nasty.

So I wondered why accordion reeds sound wrong in a concertina, and it looks as if there is a simple explanation...

When seen from above, accordion reeds have a widthways taper to them, narrowing a little from the rivetted end to the free tip. Concertina reeds are near enough parallel.

All reeds (apart from weighted low basses) tend to be thinner towards the tip, but this is more to do with tuning.

So does this taper affect the way the reed flexes along its length? Would the taper make the reed progressively stiffer (logarithmic) with the parallel reed being more linear?