The Swell knob controls the number of repeats regenerated - from a single repeat of each playback head to infinite repeats.
The Tone control tilts the EQ of the repeats from dark and fat to bright and thin. Dark settings makes the repeats sit in the background. Bright settings emphasizes the attack, great for playing off the syncopated rhythms of the multi-head arrangement.
The delay time on the Catalinbread Echorec goes from about 40ms -1000ms. And the cool thing is you can twist the Delay Time knob in real-time to get speeding-up / slowing-down, spaceship warp landing sounds!
Mix knob goes from full dry to full wet giving a lot of flexibility to use the Echorec in a variety of situations, even wet/dry rigs by setting the Mix full wet.
User-tunable modulation on the repeats that simulates the warble of the rotating platter. Or set more extreme to achieve new dimensions in chorus textures.
