Thanks all - I am quite familiar with the terms and their usage BTW. I Should have made it clear that although I am no real musician I do undertand intervals etc.

None of the above realy answers my back of the head niggle but that may well be beacause I thought I remembered something that was not realy there! Good contributions anyway.

One point I would add. Something I got from an excelent accordian player and restorer. If you block off the third note of the base side of an accordian so it will only play the 1st and 5th notes it has two effects. Firstly it makes the bass a touch quieter and secondly, you can use the same button whther you are playing the major or minor key. Not tried it yet but sounds a good idea to me anyway. As the owner of a 12 bass Piano Accordian :-)

Cheers

DtG