Zum Pitch Summator


Zum is a pitch summator for non-linear sequencing.

Video Manual: https://www.youtube.com/watch?v=xaCUfi0Zc78


Consider this: What if pitch was input, not an ordered, linear sequence, but instead was derived by summing interval values together, based on the state of gates? Zum works describing intervals, providing gates for those intervals, then producing a summed 1v/oct signal based on the gates which are high.

It provides an alternate way to create pitch sequences that are not manually input but can still can vary over time while remaining within a controlled set. The slider knobs and invert switches allow easy performance control, with a way to quickly return to a known state. To bring on the interest, gates can also be rotated, so that incoming gate signals instead trigger neighboring intervals. This can add a whole new level of describing a sequence which is both easy to perform live, and easy to get back to a prior state.


Pitches can be represented both by their note (e.g. "G", "Bb", etc.) and by their octave (1, 2, 3, etc.), giving representations such as "C3" or "F#5". This pitch/octave notations for specific notes can also be thought of as the sum of parts that combine them. For example, C3 could be thought of as 1 octave + 1 octave + 1 octave. Likewise, G2 could be though of as 1 octave + 1 octave + 7 semitones.

In the modular realm, using 1v/oct, a pitch can be expressed as a voltage, where each volt is one octave, and the semitone amount is the nearest 1/12th of a volt. Thus, G2 could be thought of as 2.583v, or described as it's component pieces as 1v + 1v + 0.583v. This is the key idea behind Zum, that a single pitch can be described as the sum of lesser parts.

The vertical sliders on Zum describe a single component part (1 octave or less). Each part has an independent gate that. When the master "GATE IN" signal is received, any components which also have a high gate will be summed to the final output.


Four gates are patched to channels 1-4 gate inputs. The first 3 channels are set to 1 octave, with the 4th channel being set to 7 semitones (or 0.583 volts). If the gates of just the first 2 channels are high, the output pitch would be 2v or C2 (1 oct + 1 oct). If the first and last gate are high, the output would be G1 (1 oct + 7 semi). If all gates were high, the output would be G3 (1 oct + 1 oct + 1 oct + 7 semi).


  1. Channels 1-8 Sliders: Each channel has a slider which can control the amount that channel will add when high. The slider amount is a multiplier that will change how much of the base range knob is added. For example, if the range knob is set to 1 oct, and the slider to 1.0, exactly 1v (1 octave) will be added when that channel is high. If the range knob is set to "3rd" (0.33v or 4 semitones) and the slider is set to 2.0, then 8 semitones will be added to the sum when that channel is high.
  2. Channel 5-8 Invert Switch: Inverts the incoming gate. Note that on these channels, no gate cable is required. Gates are normaled low, thus flipping the switch to the upper position (inverted) will make that channel always high. This can be used to, for example, always add 2 octaves to the output pitch. When used together with Rotate, this can produce interesting results.
  3. Rotate knob - Rotate shifts the evaluation of gate signals to the right for positive values, or to the left for negative values. For example, if a gate signal is high on channel 1, and rotate is set to 1, then the value of channel 1 will be used. Likewise, if the gate signal is high on channel 1, and rotate is set to -3, then the value of channel 6 will be used.


  1. Gate - Output is only summed when the gate input goes high. Output will remain until the next gate pulse.
  2. Rotate jack - Incoming voltage is added to the rotate knob. For example, if the Rotate knob is set to 2, and -5 volts is applied to the Rotate jack, the channels will be rotated by -3. Note that a combination of 5v and the rotate knob being set to max (4) will allow rotation to wrap all the way around to the starting channel.
  3. Glide amount jack - The amount of glide can likewise be controlled with pitch. Incoming CV is added to the knob position.
  4. Channels 1-8: Each channel has a unique gate input. When that signal is high, the channel amount will be added to the output. Using fewew channels will provide a basic sequence, with complexity and range increasing as the total number of channels used.
  5. Channel Modulation 1-4: The amount of pitch added can be modulated per channel for even more complex sequences. Incoming CV is added to the slider position but can be attenuated with the knob below.


Out (Sum): The sum of all channels which are high.