How does the CV section of Mutable Instruments Marbles generate random voltages?

Understanding the CV Domain of Mutable Instruments Marbles

The CV Domain of Mutable Instruments Marbles generates random control voltages for melodies, bass lines, modulation signals and harmonic structures.

Unlike traditional sample-and-hold modules, Marbles offers extensive control over how randomness behaves.

Three Related CV Outputs

Marbles provides three voltage outputs:

• X1

• X2

• X3

Each output generates random voltages that are related to the rhythmic activity of the Time Domain.

Whenever the corresponding timing output generates a trigger, a new voltage can be produced.

This creates a natural relationship between rhythm and pitch.

Voltage Range Selection

Marbles offers three voltage ranges.

Green Range

0V to +2V

Useful for:

• Small melodic movements

• Limited modulation ranges

• Narrow pitch distributions

Orange Range

0V to +5V

Useful for:

• Wider melodies

• Larger modulation movements

Red Range

-5V to +5V

Useful for:

• Full bipolar modulation

• Wide melodic spans

• Complex generative patches

SPREAD: Shaping Randomness

SPREAD is one of the most important controls.

With SPREAD centered:

• Voltages follow a bell-curve distribution

Most values occur near the middle of the selected range.

As SPREAD moves left:

• Voltages become increasingly concentrated around the center

Fully left:

• Only the center value appears

As SPREAD moves right:

• Extreme values become increasingly likely

Fully right:

• Only minimum and maximum values occur

The result is effectively a random gate generator.

BIAS: Influencing Probability

Many users misunderstand BIAS.

It does not shift voltages directly.

Instead, it changes the probability of where future voltages are likely to appear.

Turning BIAS right:

• Higher voltages become more likely

Turning BIAS left:

• Lower voltages become more likely

This creates directional tendencies without eliminating randomness.

STEPS: Quantization and Slew

The STEPS parameter performs two different functions.

Counter-Clockwise

Marbles introduces smoothing between values.

The result resembles slew limiting or glide.

Center Position

Standard sample-and-hold behavior.

Clockwise

Quantization begins.

Voltages snap to musical pitches.

Further clockwise movement progressively reduces available notes until only the root note remains across multiple octaves.

This allows Marbles to move smoothly between free random voltages and highly structured musical scales.

Randomness Modes

The CV Domain includes three behavioral modes.

Green Mode

All outputs follow the front-panel settings.

Orange Mode

X2 follows the settings directly.

X1 and X3 generate mirrored variations.

Red Mode

X1 follows the panel settings.

X3 behaves oppositely.

X2 remains neutral.

These modes create related melodic structures without requiring additional modules.

Musical Applications

The CV Domain excels at:

• Generative melodies

• Random bass lines

• Evolving harmonic movement

• Modulation generation

• Self-generating ambient music

• Controlled aleatoric composition

Conclusion

The CV Domain is much more than a random voltage source. It is a sophisticated probability-based composition system that allows precise control over the distribution, range and musical behavior of generated voltages.

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