If the Minimoog was designed to simplify modular synthesis for mass consumption, then the ARP 2600 was created to haul the whole kit and caboodle into the hands of performing musicians. Rather than limit the options with a written-in-stone signal path as Moog did, the 2600 presented a fully patchable instrument in a fairly compact package.
Offering three oscillators, noise, filter, ring mod and reverb, the 2600's fixed signal path could be defeated by patching cables into just about any point in the instrument's architecture. This meant that it was as complex as you needed it to be. Respectably complex patches could be created without plugging in a single cable, but once you chose to do so, the sky was the limit. We've heard 2600s producing everything from pseudo sequences to full on drum beats, complete with swing.
Rather than limit the options with a written-in-stone signal path as Moog did, the 2600 presented a fully patchable instrument in a fairly compact package.
The 2600 was given a leg up by its stable oscillators, and early models benefited from a filter that was all-too-similar to Moog's (at least as far as Moog's lawyers were concerned). The 2600 went through a number of revisions over the years, from its initial blue metal incarnation through the more numerous tolex-encased units to the final gaudy black and orange jobs of the early 1980s.
ARP 2600s are trading for silly prices these days. Units that were given away for pennies are selling for many thousands of dollars on the used market. Be careful, though: the earliest models are hard to repair, thanks to ARPs habit of encasing the circuits in epoxy.