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Aaron's Bass Hole - Hitchhiker's Guide to the Rainbow Machine

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Aaron's Bass Hole - Hitchhiker's Guide to the Rainbow Machine

Aaron Rogers

The Rainbow Machine is the black sheep of the EarthQuaker Devices family. It’s our red-headed step child, the wizard in the cupboard under the stairs, the one Device to rule them all; the audio equivalent of a map to Luke Skywalker that’ll take your tone to the twilight zone, open your third eye, tickle your lizard brain, and fire up your Improbability Drive faster than you can say “Zaphod Beeblebrox.” This little pink-and-white pedal has fascinated (and infuriated) guitarists since its release and been called everything from a one-trick pony to the greatest effects pedal ever made. We’re here today to dispel some of the mythology surrounding the Rainbow Machine and give you the keys to unlock this freaky Pandora’s Box of tone. And we're gonna do it on bass, because I like bass.


But What Does it Do?

The Rainbow Machine is a “Polyphonic Harmonizing Modulation Machine.” The input signal is sent into a polyphonic (ie. able to track chords) pitch shifter, which calculates harmonies from a perfect fourth below the input signal up to a major third above whatever notes you’re playing. The “Pitch” control selects the interval of the harmony, the volume of which is adjustable via the “Primary” knob. With the "Pitch" control set to noon, you'll get a wobbly unison doubling effect. Away from noon, you'll hear anything from atonal chorusing to angelic pixie trails, to a demonic subharmonic rumble.

From there, the signal is processed by a second pitch shifter controllable via the "Secondary" knob, which generates an additional octave above or below the input signal. If the “Pitch” control is set above noon, you’ll hear an octave up. Below noon on the “Pitch” knob, you’ll hear a lower octave. Use the “Primary” and “Secondary” controls to adjust the balance between your diatonic (fourth below / third above) harmonies and the octave up/down signal.

After that, your polyphonic harmonies are sent to the “Tone” and “Tracking” controls for fine-tuning. The “Tone” control rolls off top end as you turn it up, so you can dial in anything from a full-spectrum harsh noise freakout to a mellow, more subdued signal. The “Tracking” knob controls the lag between the input and effected signals – dime it and the harmonies will stack right on top of your input. Turn it down and you’ll introduce a slight delay resulting in some interesting polyrhythmic tone clusters.


And then there was one.

The “Magic” feature is the heart of the Rainbow Machine. It’s a cold, unfeeling, merciless heart, but it pumps current through the circuitry all the same. Simply put, the “Magic” is the regeneration, or feedback control for the Rainbow Machine’s dual pitch shifters. Turn the “Magic” up, and the harmonizers feedback into one another and themselves, creating pitch aliasing, which we call “pixie trails;” self-oscillation, pitch bends, and other musical mayhem. 

The Rainbow Machine has a separate footswitch for the “Magic” control, so it can be activated and deactivated at will so you can drive your rock-and-roll gravy train off the tracks, but still stop in time before it rolls off a cliff. It’s a wild ride, so hang on tight, and be sure you’re twiddlin’ those knobs while the “Magic” is engaged, because much of the Rainbow Machine’s magic – no pun intended – happens by getting hands on and adjusting the settings while you play, which is why the “Pitch” control has an Expression output for pitch bending and whammy-type effects.


So How’s it Sound?

With all the controls set to noon, the Rainbow Machine acts as a lush, yet slightly off-kilter chorus that will make your wildest 4AD Records fantasies come true. (Example 1). This is a good utility setting and should serve as a jumping-off point for further aural exploration.

In Example 2 I use the “Magic” control to sprinkle pixie dust between phrases before getting down on my hands and knees to twist some knobs and get free. The "Pitch" control is set well above noon for cascading upwards repeats.

Finally, in Example 3, I dial the “Magic” back for a harmonized chorus that increases in pitch with each repeat for cool tone-cluster echoes that lend this John Carpenter riff some spooky, just barely contained ambience.


Share your favorite Rainbow Machine applications in the comments!

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Aaron Rogers is a circuit builder and trade show rep at EarthQuaker Devices. He has a BA in English from the University of Akron, works as a freelance live sound engineer, and plays the bass guitar in Ultrasphinx.

Aaron Rogers is a circuit builder and trade show rep at EarthQuaker Devices. He has a BA in English from the University of Akron, works as a freelance live sound engineer, and plays the bass guitar in Ultrasphinx.