The second creation from ARP, the 2600 is more compact than its predecessor the 2500, and more streamlined to program. It is a semi modular analog synthesiser with each module internally connected. It features three oscillators, resonant filter, LFO (inc. sample & hold), ring mod, noise generator, built in speakers and a spring reverb. The main sound modules are internally wired for quick sound creation but patch cords can be plugged in to override internal signal routing to create more complex sounds. The attached 3620 controller keyboard improved on the older 3604P keyboard, adding two-voice polyphony, a built in LFO for adding expressive vibrato to the 2600 oscillators, portamento, envelope retrigger, pitch bend, octave transpose, and other features that greatly expanded the sound palette of the 2600.