It was defenately the VCS3, on most of the album. "On the Run" is practically a Putney solo and effects.

Additional "synths" were the Hi-Fli (gtr effect, same company as the VCS3), Farfisa , Wurlitzer , rottotoms, fuzz bass, tape loops, gated gtrs, etc.

That's how a classic album was done with 1 synth only, but using the instruments in creative ways - tapping on gtrs and bass, feedbacking, recording ppl answering 2 questions, BD as heartbeat etc.

The ARP Quadra came much later although on "Wish You Were Here" they did use an ARP String Ensemble and a Minimoog .

There simply were not that many synths back in 73-75.

Effects & cut'n'paste courtesy of Alan Parsons, who engineered @ Abbey Road, and even unknowingly named a song on the album ("Speak 2 Me"), carving in the most famous "balance-b4-recording" text.

The VSC3 is still manufacured and available if U've got 1800 pounds.

Peace,

Zooot