Musitronics Mu-Tron III
Two 9-volt batteries, a footswitch, and the vowel-like sweep that turned a box into a synthesizer.
Overview
Musitronics pitched the Mu-Tron III in its own advertising as a "mini-synthesizer" - small enough to sit on a pedalboard, and able to translate the envelope of every note you played into an articulated, vowel-like sound. The company's marketing copy promised that the harder and more percussive your attack, the wilder the result. It also said the unit worked on guitar, keyboards, drums, flute, saxophone, brasses, bass, mandolin, and even microphone. That was advertising, not a review. But the design did something a standard wah couldn't: it tracked your playing dynamics automatically rather than waiting for your foot.
The core of the thing is an envelope-controlled filter. Play a note, and the Mu-Tron III reads the "volume picture" of that note and sweeps a filter in response. That produces the vowel-like formant shift that made it famous. The DRIVE switch flips the direction of the sweep, up or down in pitch. That is the difference between the familiar wah-style rise and the "staccato snap" of an inverted trajectory. The MODE switch selects Low Pass, Band Pass, or High Pass, so you can accent the bass, the mids, or the treble region of the signal. RANGE emphasizes either the vowel-like low content or the overtones up top. PEAK sets how sharp the filter is, from a subtle accentuation through a distinct vowel sound to high-resolution filtering that picks out individual overtones. GAIN is both the volume control and the sensitivity control for the effect, which is why the manual tells you to set it by ear while playing strong, percussive notes.
The spec sheet is modest but specific. Gain is variable from 0.1 to 40 when driven from a low-impedance source. Input impedance runs from roughly a megohm at the lowest gain setting down to 3.3K ohms at maximum gain. Minimum input signal for full Mu-Tron effect is 1.5 mV from a 600-ohm source, and output impedance is 600 ohms. Maximum undistorted output is 3.6 volts RMS. The unit weighs 3AA lbs. without batteries and measures 8½ inches long, 5 inches wide, and 3½ inches high, a substantial chunk of metal and circuit board by modern pedal standards. Suggested retail was $99.95, and it was made in the U.S.A. The warranty was a full year on parts and labor.
Power comes from two NEDA 1604 batteries (the 9-volt you know) or the optional Musitronics Model PS-1 battery eliminator, which connects via a keyed 3-pin socket on the rear. The manual is unusually candid about battery behavior. The battery in the holder with the red lead drains considerably faster than the one in the black-lead holder, thanks to unequal current drain. Owners should expect to replace the red-lead battery two or three times before both need changing. Alkaline cells are recommended, especially in that red-lead holder. The first sign of a dying battery is a reduction or loss of the wah effect, sometimes with high-frequency oscillation, so try fresh batteries before assuming the unit is broken. If you leave the PS-1 connected with batteries still installed, the eliminator will charge them, which the manual warns can lead to leakage or even damage to the battery cases. Musitronics' advice: pull the batteries when running on the PS-1.
Controls are a POWER on-off switch, the DRIVE switch, the RANGE switch, the MODE switch, GAIN and PEAK knobs, and a FOOT switch that bypasses the effect entirely. With the effect bypassed, the Mu-Tron III still works as a flat preamp whose gain you set with the GAIN control. Push that gain high enough and you can overdrive your amplifier into distortion on purpose. The manual provides starting settings for guitar: High Pass, PEAK at 10, GAIN between 1 and 4, RANGE low, DRIVE up for a lead sound; Band Pass with GAIN 1-4 and DRIVE up for funky rhythm; High Pass with GAIN at 10, RANGE high, DRIVE down for distortion. A "guitar beat phenomenon" trick is documented too: play the same note on two strings, bend one slightly out of tune, and the beat frequency triggers the effect on each pulse.
Two Mu-Trons can be cascaded: instrument into the first, the first's amplifier jack into the second's instrument input, the second into your amp. Run one with DRIVE up and the other with DRIVE down and you get a stereo effect that sounds like two different instruments playing at once. The manual also notes that octave dividers and sub-octave devices pair particularly well, ideally placed between the instrument and the Mu-Tron.
EQ Magazine (December 1999, p.39) listed the Mu-Tron III alongside the Mu-Tron Bi-Phase in a roundup of classic effects still in use. EQ Magazine (September 2007, p.30) documented the pedal in a modern recording chain: a Fender Telecaster into an old Musitronics Mu-Tron III envelope filter into a small Marshall combo. The producer noted that different guitar and amp combinations were tracked to separate channels so the band could pick and choose sounds during mixdown.
The Mu-Tron III is not a subtle pedal. The effect is driven by attack, so a limp note produces a limp sweep. The controls interact in ways that take time to learn, and the battery situation is fussy by modern standards.
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