This is fascinating. As soon as musicians move away from a written version and tunes go feral, intentional and unintentional changes creep in. It happens naturally and doesn't usually cause any anger or mud-slinging; I think it's an excellent example of the folk process in action and keeps the music alive. In a session, people will generally follow the player who's leading that particular tune on that particular occasion.

In The S of M I think the change of structure to AAAA-BBBB is rather like adjusting pronunication to local dialect, just as an English singer may change Scottish words to English ones ('maid' for 'lass' and so on). Your band's A-A-A-A-B-B-B-A is more common in tunes from the North of England, particularly from Northumberland and the Borders; is that because it includes a Scottish/Canadian and a Northumbrian piper?

The key change from A (fiddlers, especially Scottish ones, will always slip into A if you don't keep a close eye on the blighters) presumably came about to make life easier for melodeon and Anglo concertina players. G is the most common session key and is closer to A in pitch.

I like playing S of M in D because it sounds better to me than G and doesn't shut out the melodeon players. (A wouldn't be a problem for me: English concertinas are fully chromatic and it's always nice to use the less familiar reeds because you can't ask the chap who tunes them only to tune the ones you actually play.)

Very rarely, tunes suffer changes which don't improve them. From a personal point of view, I don't enjoy the B music of The Quaker being grafted onto the A music of Walter Bulwer's No. 2 polka because it robs us of two good tunes and bereaves the tunes that both are frequently played with; I also don't enjoy the B music of From Night Til Morn being cut down to eight bars from twelve, although I can see why it happens.

Having said that, the changes don't ruin the tunes for ever; it's not like drawing a moustache on the original Mona Lisa, but only on a copy. You can always go back to the original, or any point between now and then.

Valmai