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You can find a
demo by Steve Fisk at the 2011 PNW SynthFest demoing his ARP 2600 posted here (see
this post for additional videos of the event). P.S. If you aren't familiar with Steve Fisk, see
this Wikipedia article. His Yamaha CS60 went up for sale
back in 2013.
According to
this auction by Salamander Labs, his 2600 is up for sale. I have no way of verifying, so do your due diligence if you are interested. Note in the video linked above there is a green monkey sticker on the front panel. It's missing from this ARP 2600 but you can see a slight discoloration where it would have been. As always, who knows...
Details via
the listing:

"Ok, this is it. An Arp 2600 with keyboard used extensively as a live and studio instrument by Steve Fisk, whose comments and the unit’s pedigree are below. This instrument has been used on the road internationally, in studio, and live performance settings, and as a result has some cosmetic scratches. The power supply caps, speaker amp driver transistors, key bushings, and a few key springs have been replaced…and the shittyist plug ever used for a keyboard has been replaced as noted below….otherwise it is original. It is fully discrete, and the circuit boards are NOT epoxied so it can be serviced. A full factory calibration was completed by Gemma at Sound Audio Repair in Olympia, Wa…"
"From Steve Fisk;
My 2600 is the first synth you see on the Arp 2600 Wikipedia page. I am the original owner. I bought the synthesizer in 1976. It was my primary instrument for years. I wrote and performed several noisy live pieces with the ARP. It was also my “jam” instrument for many improvs in Olympia and Seattle in the late 70’s. It was a key part of my live setup for Pell Mell, Pigeonhed, Customer Service, and Tiny Holes. It is also featured in much of my studio work with Pell Mell, Soundgarden, Pigeonhed, Reggie Watts, Unwound, Some Velvet Sidewalk and Seacats. The beast was my goto box for 808 kick drums(see Soundgarden’s “Spoonman” remix). It also did duty on several film soundtracks and corporate work. In 1995 the Jones plug that connected the keyboard to the main frame was replaced with a robust milspec connector by Omega Intl, a vintage synth service run by an ex roadie from the Moody Blues. It is in excellent working order despite some well earned cosmetic blemishes. I’m going to miss the spring reverb, a great resource for sound effects."