This is a fine filter for those on a budget, and well worth considering if you can’t justify the hefty price of the Mu-Tron III. In 1995, Electro-Harmonix commissioned Beigel to help them with their popular Q-Tron filter. HAZ Laboratories produced a reissue named the ‘Mu-Tron III+’, yet despite looking like an exact replica of the original Musitronics pedal, it is not an authorised version and, according to Mike Beigel, the circuit is not the same. Part of designer Mike Beigel’s technical genius was to use opto-isolators to control the filter, which is the most common reason why MuTron clones that lack these integral features never quite hit the spot. This is probably one of the most copied pedals ever, though it seems few have come close to fully replicating its sound. Long exposure of a musician adjusting dials on a pair of Musitronics Mu-Tron III effects pedals and Moogerfooger analog effects modules, taken on OctoAlternatives Like all envelope filters, the level of ‘quack’ is controlled by how hard you hit the strings on your bass, so you’ll need to adjust the gain control accordingly. The range switch adds the filter sweep to the low or high end of your signal, and for those classic auto-wah sounds put the drive switch in the up position. Using the peak knob, you can adjust the amount of the filter that’s being added to the signal, and the gain control doubles as both a volume and sensitivity control.

The mode control selects a low pass, band pass or high pass filter sweep. The Mu-Tron III has six simple controls – three knobs and three switches – which allow you to tweak the filter in a number of different ways. The Mu-Tron was still produced by ARP for about a year before the company went under in 1980.

Musitronics continued to make the Mu-Tron III, along with other phase and octave effects, until 1979, when they sold the company to ARP. The Roman numeral ‘III’ was apparently Beigel’s favourite number and was adopted from the start – versions ‘I’ and ‘II’ never existed. The original prototype was called the ‘Auto-Wah’ but was renamed before initial release as the ‘Mu-Tron’, a contraction of the company name.

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