The people at Moog Music have topped themselves once again with another addition to their Moogerfooger line. The MF-105M MIDI MuRF is a combination of the MF-105 MuRF and the MF-105B Bass MuRF, featuring the same CV (control voltage) inputs offered on other models but with the expanded capabilities of MIDI. The MuRF (which stands for “multiple resonance filter array”) is an analog effect unit that features eight resonant band-pass filters with individual gain controls, along with an Animation section for modulating the filters by means of Mix, Envelope, Patterns and Rate knobs. The frontpanel controls are rounded out by a Drive control to adjust the input volume of the signal and an Output control. On the back panel there is a MIDI In, Audio In, Audio Left/Mono and Right outputs, plus an array of CV inputs, including Tap/Step (for tempo input), LFO/Sweep, Rate, Mix, and Envelope.
The MIDI MuRF provides both the Mid filter bands of the MuRF and the Bass filter bands of the Bass MuRF, and the eight frequency bands change when you switch modes. In both modes, all bands are resonant. In Mids mode, all are band-pass, but in Bass mode the first filter acts as a low-pass with a cutoff at 110Hz (to allow bass players to achieve lower frequency ranges) while the rest are band-pass. The other seven resonant filters offer frequency ranges from 160Hz to 1800Hz. This mode is not just for bass players, though—guitarists can utilize it as well, especially those who downtune. I found this mode useful when playing lower notes, as it allowed the higher ones to be less colored by the effect.
In Mids mode, all eight bands act as resonant filters, with frequency ranges of 200Hz to 3400Hz. This mode is not only useful for guitar, but for other instruments such as synthesizers and voice. Any instrument with a strong midrange will benefit from the rich harmonics of this mode. The Filter Matrix mode of the Electro-Harmonix Deluxe Electric Mistress came to mind when playing around with the filters in Mids mode. At some points, the harmonics became very shimmery and bell like, but softer than the Deluxe Electric Mistress.
Each filter has a slider that adjusts the gain of that filter: with the slider all the way down the filter is at 0, and all the way up the filter is at maximum. Since these are resonant filters, the signal is boosted at the center frequency. Unlike with a graphic equalizer, the filters are tuned to not overlap, which brings more warmth and color to the tonal palette. I took a lot of time exploring the ranges of the filters when first plugging into the MIDI MuRF. With its ability to achieve a broad spectrum of frequency ranges, from warm bass to punchy midrange and shimmering highs, the MF-105M provides a tonal palette that is highly versatile.
The root of the MIDI MuRF’s Animation section is an eight-channel sequencer, with one channel for each filter. The patterns trigger the envelope generator that shapes the volume of each of the filters, creating the sequence. With 12 patterns available for each frequency mode, there are 24 patterns total—although patterns 1 and 12 are fixed, allowing the user to utilize just the filters without any animation. Only pattern 1 has no animation, but like the rest, it can be overwritten with the included Pattern Editor software (more on that later).
The Envelope control adjusts the attack and decay of the envelope generator circuit, which acts as a square wave. When the Envelope control is at 12 o’clock, the attack is sharp with a smooth decay. Turn the Envelope control counterclockwise and the decay decreases, causing the notes and patterns to become choppier. Go clockwise past 12 o’clock and the sound flips, because the attack and decay have become so long that the filters are crossfading into one another. The Envelope control is the key to shaping the way the filters react to the notes and patterns. I had great fun creating everything from choppy rhythms to resonant soundscapes.