That's interesting ... if you were listening to a band play, wouldn't different instruments play on different verses? ... or is it that with each voice that's being used the melody is exactly the same ... that situation gets to ME ... I'm short on my music theory and chord structure/substitution and harmonies, but I can do a fairly competent job of taking an ad-lib solo around the basic chord structure of the song so it sounds somewhat different when using a different voice ...