Used it once to noise gate, with no other equipment, so a group of people in a studio, individually miked and wearing headphones, could have a "talk show" conversation with phone guests.

Used the Arp to gate the telephone line being recorded, whenever someone in the studio spoke; they'd get recorded in full fidelity on the other track, so the phone only added distortion.

Then, when the phone caller spoke back, Arp turned up the input and even compressed it a few dB. Could have also filtered out 60 Hz hum if it was a problem.

Also used it to generate 67 kHz carrier, modulated by audio (both AM and FM) to test FM SCA receivers.

Even used it as intrusion alarm. When we'd leave the house (or the wife sleeping alone while I worked late), I'd set the 2600 so it sounded like the end of the world! Fast warbling alarm sirens, huge slow air raid sirens, klaxons, explosions! Then I'd pot up the internal amp voltage, with most of ten volts positive into the final mixer amp, which would turn it up loud (Silvertone amp with two twelves, like the Velvet Underground used to use). Put a plug in that hole, and the synthesizer is muted. Attach that plug to a ten foot patch cord, looped around the knob on the front door. Open the door, pull the plug, hell rains down. Unless you know to open it a few inches, reach in and unhook the wire loop from the knob.

Just my way of saying the versatility of this wonderful machine is limited only by what you need it to do.