Make Noise XPO: Dual 1v/Oct Inputs—A Patchable Playground

The Make Noise XPO stands out in the oscillator landscape by offering not just one, but two 1v/oct inputs—a feature that’s far from standard fare in Eurorack. Right from the start, the video frames this as a deliberate design choice, inviting patchers to think beyond the usual single-pitch control. The second input isn’t simply a copy; it’s an exponential frequency modulation input, summed with the primary pitch CV, and crucially, it’s unattenuated, meaning it responds directly to whatever voltage you throw at it.

This opens up a world of possibilities for creative patching. The presenter suggests thinking of the second input as a transpose control, but it’s equally at home as a source for audio-rate FM or stepped voltages. By patching in an attenuated audio signal, you can achieve classic exponential FM effects, with the depth scaling as the input amplitude increases. The XPO’s architecture encourages experimentation, making it a playground for those who want to push their oscillator’s pitch control into new territory.

With both 1v/oct inputs available, the XPO lets users blend traditional pitch sequencing with exponential FM in a single module. The video demonstrates how sending a DC voltage—like a random stepped CV or a sequencer—into the second input allows the oscillator to hold a static pitch, thanks to the DC-coupled design. This is a key distinction from linear FM, where static voltages become transients rather than steady shifts.

The ability to combine sequenced pitch with FM opens up dynamic sound manipulation. For instance, you can sequence the main pitch while using the second input for transposition or additional modulation. The result is a more expressive oscillator, capable of both precise melodic control and wild, evolving timbres, depending on how you patch it. The XPO’s dual-input design encourages users to explore the grey area between stable pitch and controlled chaos.

The video moves from theory to practice by showcasing how the dual 1v/oct inputs can be used for hands-on transposition and tonal variety. Using a Make Noise René sequencer, the presenter patches the X channel for the main sequence and employs the Y CV for transposition duties. By manually selecting transpositions on the René’s latch page, it’s possible to inject key changes and interval jumps exactly when desired, adding a performative element to sequencing.

This approach isn’t just about shifting pitch for the sake of it. The video points out that the rate and interval of transposition can dramatically affect the musical outcome. Fast, arbitrary transpositions can dissolve a sense of tonality, while restricting transpositions to octaves or simple intervals keeps the sequence grounded. The quantize page on René is used to limit transpositions to specific notes, demonstrating how even rapid octave shifts can maintain musical coherence, while adding more notes introduces a sense of key changes and harmonic movement.

Pushing further, the video explores how alternating and stacking sequences through the XPO’s dual inputs can yield intricate, evolving patterns. By clocking two René channels at the same rate but out of phase, each sequence takes turns running while the other is paused. The clever twist is that the last note of the stopped sequence acts as a transposition source for the active one, effectively stitching two melodic lines into a single, longer sequence with built-in variation.

Varying the lengths of the two sequences introduces continual shifts in transposition, creating a self-modulating patch that evolves over time. The result is a set of melodic variations that remain related to the original material but never quite repeat in the same way. This technique highlights the creative potential of the XPO’s dual 1v/oct inputs—not just for FM or transposition, but as a means to interweave multiple musical ideas into a richer, more textured performance.