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Review: Mutable Instruments Marbles, Random Sampler Eurorack Module
Benjamin Chilton on Wed, April 25th 0 comments
The beauty of modular gear is its ability to be manipulated in almost infinite ways using control voltage. Could Mutable Instruments Marbles be the perfect way to do just that?

Mutable Instruments' new Eurorack modular offering is an extremely useful random CV source. Utilising elements from Mutable’s previous models as well as a whole host of new features, this module can be used for a wide range of functions. It offers rhythmic triggers, a jittered clock source, quantised sample & hold and a Deja-Vu feature which allows for Turing Machine-style looping of all these random sources. 

Marbles is very much a module of two halves. On the left hand side, pots and buttons relate to clocking and trigger operations. These take the form of 3 different modes, sending pulses from the 3 outputs at the bottom left on the module (t1, t2, t3). In all modes the t2 outputs a steady clock signal from either an internal or external clock. This can be /4, x1 or x4 of the master clock source. Using the Jitter parameter it is possible to take this clock signal from a steady pulse through some light shuffle right the way to sporadic, unpredictable bursts. Perfect for emulating the rhythmic failure of human drummers, should you wish!

The 3 modes of the T section (accessible from the button to the left of the Rate control pot) are as follows:

  • Clocked coin toss - Green:

For each trigger generated from t2 a coin is tossed to decide whether a trigger is also output from t1 or t3. This mode is very similar to Branches, with Bias weighting the coin one way or the other.

  • Random ratcheting - Orange: 

An extremely fun mode which uses randomly generated numbers to multiply or divide the clock signal on t1 and t3. The further Bias is turned, the more extreme division and multiplication can be achieved. Combine with a touch of Jitter and you’ve got some great funk breaks.

  • Kick and Snare - Red:

This mode replicates the first 2 channels of Mutable’s map-based drum sequencer, Grids. Within this mode t1 and t3 output patterns based on standard kick and snare rhythms. Run some modulation into the Bias CV input and you’ll be swimming in generative drum patterns.

The right hand side of Marbles takes charge of random voltage generation. The X outputs at the bottom match up to their respective trigger outputs, only sampling a new random voltage when its counterpart outputs a trigger signal. The two are very effective when run into the 1V/oct and envelope of a synth voice patch or into the modulation and trigger inputs of a drum module. We’ve had Marbles paired in this way with Mutable Instruments Rings and let me tell you, it sings!

By using the button above the Step pot the X section can be flipped through a couple of different voltage ranges: 

0 to +2v 0 to +5v -5v to +5v

The Spread parameter allows control over the difference of voltages within this range. This can go from a small fluctuation in voltage (great for bass lines or subtle modulation) all the way to a full 10V in the -5v to +5v range for unpredictable jumps and sharp changes. Steps is used to control the slewing and quantization of these voltages, fully counter clockwise and a hefty, drunken slew is introduced. With Steps at 12 o'clock the X outputs will run a standard sample and hold function. Clockwise past the centre and these random voltages start to become more and more quantised, from a full chromatic scale to octaves. Between this it moves through a C major scale, stripping out notes until only the octaves remain. Perfect for the more ‘musically challenged’ modular user.

The Y output from the centre constantly outputs a heavily slewed voltage generator, running at 1/16 of the master clock speed. This can be adjusted of course in true Mutable Instruments style by holding the Length button and shifting the pots around.

Arguably Marbles’ most intuitive and musical feature is its Deja-Vu section. This allows the user to loop any generated CV patterns as well as ‘sampling’ external CV which can then be quantized, slewed, shifted and attenuated in the same way as any internal voltages. 

The Length knob controls the number of bars looped using a division of the master clock ranging from 1 to 16. With T and X locked Deja-Vu can be used to allow new random voltages and triggers into the loop when rotated counter clockwise. When turned clockwise Deja-Vu will start to randomly skip around the loop, a simple way of adding subtle (or extreme) glitches to your CV pattern.


All of these inputs have an input for CV modulation, making cross patching the Marbles a simple but effective way to get regenerating modulation, melodies and rhythms. Marbles is a great module for random generative patterns, but also works fantastically as a hands-on performance tool. 

Price: $359 USD / £259 GBP

Pros: Extremely powerful for both modulation and sequencing. Quick way of generating unique patterns. Works as an external CV processor. Very hands-on.

Cons: All scales are rooted in C by default. A little too wide for some smaller cases. Works best with stackable or splitter cables.


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