John in Kansas - I understood you the first time, about the harmonics not being in tune. With all due respect I don't believe it, but I am willing to be educated. Can you supply references to evidence for this?

I can hear the 2nd and third harmonics of notes from my concertina quite clearly and they don't seem to be out of tune.

As for difficulty of synthesis, the strings of a piano, especially the low end, definitely have their overtones badly out of tune i.e. not simple ratios, so that should be difficult to synthesise too. Of course good synths use samples of real instruments anyway but I digress...

Anahata