Marc Doty (YouTube channel AutomaticGainsay) has created an excellent series of videos about the Arp 2600.
The company Arturia has created a virtual software version of the 2600.
Year Released: 1971
Keyboard: 49 keys
TTSH ARP 2600 Clone 2017 Black ($3,400)
ARP 2600 TTSH 2017 Custom Case ($3,800)