Decent mixing of masters is an art. Motown had it in the 60's because all their mixes were designed for small radio speakers and so the mixes were designed to belt out over a tinny speaker. That's why the tambourines, bass and snare are always so upfront. When everything started going to 16 and 24 track by the late 60'a and 70's and home systems got much better along with big club systems, then different skills were required. I learnt all about mixes by listening to the first two Trammps albums on Atlantic ("That's Where The Happy People Go" and "Disco Inferno") which I don't think have been bettered for scintillating Philly mixes. Moulton was undoubtably the master, no question. Once he paved the way then plenty of great mixers followed. As a DJ my favourite ever mixes are The Trammps "That's Where The Happy People Go", T. Connection's "Do What You Wanna Do", "At Midnight" and "Saturday Night" (all Alex Sadkin and genius mixes) and Gwen Guthrie's "Seventh Heaven" (Larry Levan).
But, hey, I could list 100's.....
Ian D