Mod Squad: West Oakland Music Systems Skipmin

Give your piece some chance with this quad gate skipper
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Give your piece some chance with this quad gate skipper
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One of the secrets to creating rhythmically complex music with a modular is to add a level of indeterminacy to the triggers and gates, typically by introducing logic or probability circuits. With the Skipmin ($150), West Oakland Music Systems (westoaklandmusicsystems.info) has created an elegant and relatively low-cost way to inject musically useful chance elements into your patches.

One of the most compelling things about the Skipmin, which the developer refers to as a “quad probabilistic gate skipper,” is how easy it is to use. The module has four inputs that accept triggers and gates up to 10V, and four outputs, each with a dedicated mute button.

In addition, each output has a Skip control, which determines how likely the input will go through. Once an input voltage reaches its max level, it is subjected to a probability test (based on the setting of the Skip knob), and if it passes the test, the corresponding output delivers a +5V signal that lasts as long as the input signal stays high. An LED at each output lights when a signal makes it through.

When the knob is set fully counter-clockwise, there is a 0% chance the signal will pass; turning it fully clockwise sets the probability to 100%, so that the signal is always present at the output. The simplicity of the Skipmin is also a result of the fact that you can’t visually set the probability amount (except at the extremes), so you have to play it by ear, so to speak.

Although the outputs can be used discretely to process four individual signals (input 1 to output 1, input 2 to output 2, etc.), the inputs are normalized to the outputs in numerical order. For example, patch a trigger to input 1 and it is available at all four outputs. Then if you add a trigger to input 2, that trigger now goes to outs 2, 3, and 4 while input 1 goes only to output 1. Consequently, the normalization scheme lets you send one clock to several outputs, each of which can have its own probability setting— sweet! Moreover, if you mute the primary channel of the incoming signal, the normaled channels that follow remain active. Each Skip knob glows blue until you press its corresponding Mute button; then it goes dark.

In addition to rhythmic chores, the Skipmin can also be used as an ersatz waveshaper. Patch an audio-rate (20 Hz or greater) signal to an input and you are treated to glitchy results that begin to resemble bit reduction as you turn the Skip control counterclockwise. Using a sequenced melody patched to input 1, I set the Skip knob to 12 o’clock for outputs 1 and 2, then panned each output to different speakers. The timbre coming from the two outputs differed because of the probabilistic routines, even when the Skip knob was at a similar setting. As the sequence progressed, crunchy dropouts would occur at different times from either channel, creating a nice stereo effect.

Although there were times when I wished the module offered CV control over the Skip amount, one of the charming things about the Skipmin is that the interface is so straightforward. And, it requires much less rack space than bigger, more complex modules offering probability features.

The Skipmin is definitely worth checking out if you enjoy making beat-based and West Coast-style patches that have a variable level of unpredictability.

Special thanks to I/O Music Technology (io-mt.com) for loaning us the module for this article.