Dave the gnome wrote; "I have figured out the chorus of Kenny Rogers 'The Gambler'. Quite fancy a country song on the squeezebox:-) "

Some people can be a bit precious about what should or shouldn't be played/sung/accompanied/etc. My own practice is to have a go at anything that strikes my fancy and if it works, goodoh! Being an anglo player with more competence at melodies than harmonies I might be out of place on this thread but I've been playing (and singing some of the words of) Slim Dusty's "The rain tumbled down in July" for some years now. For those of you north of the equator, Slim Dusty has been Australia's best known Country music singer for a couple of generations and that song is reputed to be the first he ever wrote and performed publicly.

Your reference to "The gambler" is apposite for me. A few months ago I was teaching some students how to use surveying levels and to book the readings using the 'rise and fall' method. A student from a few years before had written a blues song about this week-long school and the current students decided to write their own. It turned out to be a parody on "The Gambler", with the chorus;
"You got to know when to backsight
Know when to foresight
Know how to book them
When the staff is straight.
You'd better centre your bubble
Or later there'll be trouble
You never read your level
'Til the level's plumb."
And It'll give me great pleasure to be putting in an accompaniment on the concer for them.

Captain Birdseye wrote;
"Peter generally played melody and added a few chords here and there, he also had a drone button which he operated with his thumb, he was also a great harmony singer,Young Tradition, so i guess he might sometimes play harmonies."

If this is about Peter Bellamy it is certainly a good description of how he played; as mentioned above, he played an Anglo concertina which had a three-row keyboard and was thus chromatic. Unlike the English keybord, such Anglo concertinas usually had a button for the left thumb and often it was pitched (in both bellows directions) at the tonic for the lower of its home rows, allowing it to be used as a drone. On an English, any button can be so used once you've trained your fingers.

Dick also wrote;
"I would keep away from concertina sites they are full of pedants and assholes."
You may have much more experience of them than I, Dick. I contribute to only one and, without exception, all the contributions to it that I've seen have been polite, constructive, informed and helpful. Some may regard my previous paragraph as a perfect example of the sort of pedantry to be expected on a concertina site but it's offered in a spirit of helpfulness.

Cheers, Rowan (who's currently on leave, at last)