In this article, I will share a unique technique to retune a fixed-pitch kick sound using the Qu-Bit Prism’s comb delay mode, enabling full integration with modal guitar compositions. This method allows the harmonization of unmodifiable percussion sources with dynamic, phrygian or chromatic tonal environments, particularly when your guitar is processed separately through spatial or phaser effects.

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Context & Objective

Many Eurorack modules feature internal sound sources that are not pitch-adjustable, like the kick in the Noise Engineering Cascade. By default, the kick is tuned to approximately F (87.31 Hz) and cannot be changed directly. However, if your guitar is being processed through a module like the Doepfer A-101-8 Phaser and set in a different scale (e.g. C Phrygian or D Hypophrygian), the fixed F may sound dissonant or disconnected.

The solution? Use the comb delay mode of the Qu-Bit Prism to spectrally shift the perceived pitch of the kick without affecting the original source. The comb delay introduces a series of phase-based reinforcements and cancellations that act like a pseudo-pitch shifter.

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How It Works

The Prism’s comb delay works by mixing a delayed version of the signal with itself, creating constructive and destructive interference patterns. The delay time determines which frequencies are emphasized. This turns the Prism into a resonator that can « tune » the kick by emphasizing partials that correspond to different musical notes.

For example:

• A delay time of 11.46 ms emphasizes G (98 Hz)
• A delay time of 13.62 ms emphasizes D (73.42 Hz)
• A delay time of 15.29 ms emphasizes C (65.41 Hz)

This spectral shaping allows you to align your kick with your guitar’s key.

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Comb Delay Pitch Table

Here is a reference table you can use to dial in precise delay times to match your target scale:

Target Note	Frequency (Hz)	Delay Time (ms)
C	65.41	15.29
C#	69.30	14.43
D	73.42	13.62
D#	77.78	12.86
E	82.41	12.13
F	87.31	11.46
F#	92.50	10.81
G	98.00	10.20
G#	103.83	9.63
A	110.00	9.09
A#	116.54	8.58
B	123.47	8.10
C2	130.81	7.64

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Creative Expansions

• LFO Modulation: Slowly modulate the delay time with a sine LFO to create microtonal drift or ritual-like pulsing.
• VCAs & Attenuverters: Use a VCA or a passive attenuverter to control how much modulation affects the comb delay, keeping it in a safe tonal range.
• Guitar–Percussion Dialogue: The guitar remains harmonically stable while the kick adapts, creating a dialogue between tonal center and percussive drive.

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Application in ‘Ornamants’ by Zi Iacchos

This technique was used in the first track of the new experimental project Zi Iacchos, entitled « Ornamants. »

The foundation of the piece is in E (Mi), with the Zlob Modular Double VCO operating in exponential mode. The tonality then shifts during a bridge passage to B-flat (Bb) by switching the Zlob VCO into linear mode. This moment opens the space for a guitar solo phrased like an ornamental chant, echoing the title’s meaning.

This harmonic modulation allows the kick—originally locked in F—to follow the emotional flow of the track using the comb delay’s pitch-shifting capabilities.

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Spiritual Framework: The Influence of the Heart Sūtra

The composition draws philosophical and spiritual inspiration from the Heart Sūtra (Prajñāpāramitā Hṛdaya), a central Mahāyāna Buddhist text emphasizing the illusory nature of form and identity. Just as the sūtra declares, « Form is emptiness; emptiness is form, » the sound in « Ornamants » is shaped by the absence of direct pitch control—only to be sculpted through delay, resonance, and perception.

This technique resonates with the sūtra’s core teaching: transcendence arises not by altering the object, but by transforming the field of perception itself. Here, the comb delay acts like the insight of prajñā: it does not change the kick, but re-contextualizes it to reveal a new harmonic truth.

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Conclusion

This technique provides a powerful way to transform a rigid percussive sound into a harmonically adaptive instrument within a modular setup. Especially for compositions inspired by sacred modes or sūtric rhythms, this spectral tuning can bring together the raw pulse of electronic percussion with the tonal subtlety of guitar-based phrasing.

Zi