Anne, it's the lyrics that MAKE those songs. Of course I change the pitch. My crusty ol' baritone can't even do 'em an octave down from you two any more. I bumble around the guitar in my own way and I have to make 'em sound recognisable as a solo rather than a duo, which leads to some interesting bits where I effectively have to swap between your line and Mary's mid-phrase but mess with your lyrics? NEVER. I wouldn't be singing the same song.