I have just been listening to Kevin Ayers' "Joy of a Toy" which features a fair amount of Mark II. It made m think of how tron styles have changed. Up until the Moody Blues and King Crimson, the mellotron was often used quite dry and played in a more staccato or at least non legato fashion, sounding much more lo-fi and unrealistic. I'm thinking of the way Stevie Winwood, Manfred Mann used Mark IIs as well.
Robert Fripp, Mike Pinder and Woolly when he got an M300 used a lusher, wetter more legato, and chord based sound and that seems to have persisted to the present day.
I quite miss the simpler more percussive sound of the 60's.
Mark