From Grosvenor Studios, London (inventory number pending)
Sold in 1970, this monophonic synth was Arp’s answer to the Moog modular synth. The Arp 2500 was a complex but very flexible machine, controlled by moving switches on its many 10 x 10 patch boards. Only 100 of these synths were made. The Arp 2500 was superseded by the far more popular Arp 2600 which had fewer knobs and buttons (and was thus a more usable gigging instrument). Stevie Wonder was one of the most notable exponents of the Arp 2600.
The Arp 2500 was used by Herbie Hancock, Pete Townsend, John Michel Jarre and others. And it was also used to play the five note melody that called out to aliens in Spielberg’s sci-fi film Close Encounters of the Third Kind (1977). The synth technician you see in the Spielberg film is actually Philip Dodds, vice president of Arp at the time. Spielberg offered Dodds the role when he brought the Arp to the set for filming.
David Morley demonstrating an Arp 2500
(via buchla300, YouTube)
Stevie Wonder demonstrates his Arp 2600 to David Frost
(via Synthfool, YouTube)