Hermetic Modular

Alchemy Lab / Capicola

Capicola

Real-time Time Stretcher

A collab with Heavylight Industries

Time stretching, in real time! Capicola stretches audio out while staying aligned to the rhythm of the input. Give your signal a glitched-out character without missing a beat. Capicola turns audio into envelope followers and triggers that can either self-modulate or feed to the rest of your rack. It’s a dynamic audio effect and CV utility in a 12HP package.

Capicola in a Eurorack case with its labeled controls and glowing amber LED rings

Slice, stretch, shift, distort

A novel time stretching algorithm

At its core, Capicola is the hardware implementation of “Extrema Sampling,” a novel data compression algorithm that reduces uniformly sampled 48kHz audio into non-uniform “Keyframes” of local extrema (peaks and valleys of the signal). The “Quality” knob determines the level of data compression applied in a continuous, modulatable fashion. It’s not bitcrush, it’s not downsampling. It’s a tape-like degradation the likes of which exist literally nowhere else.

This non-uniform sampling scheme, not dissimilar from Keyframe Animation in Blender 3D, is the basis for Capicola’s novel approach to “Overlap Add” time stretching in which the spacing between keyframes informs the granular crossfade duration. This inherently preserves the beats and tones, leaving the user with a “Grain Size” macro control.

Capicola also offers a novel approach to nonlinear distortion, again enabled by the keyframe representation. The distortion is applied to the keyframes in the “sparse domain” before the final interpolation, resulting in a naturally alias-free distortion that requires no oversampling and can facilitate many wild nonlinearities with ease.

  • Capicola in a Eurorack case beside a sampler
  • Close-up of the Alchemy Lab analog circuitry

Performance features

Real time stretch, real time play

Each of Capicola’s main controls is fully modulatable from either the internal envelope followers or external CV, with dedicated attenuverters for each control. The envelope follower is an excellent source of “self” modulation, and easily leads to evolving, dynamic patches with a mind of their own.

The “Threshold” control allows the user to easily create “glitch fills” by temporarily disabling the beat snapping. The settings of stretch, pitch, and grain size lead to anything from ethereal washes of time-stretched sound to beat-synced looping segments.

The visual feedback engine of Alchemy Lab makes multiple pages of controls a pleasure to use rather than an exercise in memory. Capicola utilizes four color-coded pages to offer settings that are wide enough in scope to offer supreme flexibility but only when the user needs it. The main controls are knob-per-function on the main panel, and everything else acts in service of them.

Capicola keyframe sampling: audio, feedback, and detector routingAudio input splits into a dry path and a sum feeding the keyframer. The wet signal feeds the output mix and a feedback loop through a saturator, bandpass filter, and feedback gain back to the input sum. The input detector taps the summed input; its trigger combines with Trig In to slice the keyframer and is available at Trig Out 1. Its envelope is Env Out 1. The output detector taps the post-mix output and provides Trig Out 2 and Env Out 2. Processor controls are listed in their footers. Quality, Pitch, Stretch, Character, Drive, and Grain Size control the keyframer. Character controls the saturator; Cutoff controls the bandpass filter. Both detectors have Cutoff, Smoothing, and Threshold controls.FEEDBACK LOOPWET SIGNAL RETURNS TO INPUTDryWetAUDIO INEXTREMA SAMPLINGKEYFRAMERQuality · Pitch · StretchCharacter · Drive · Grain SizeMIXAUDIO OUTSATURATORCharacterBANDPASSFILTERCutoffFeedbackTRIG INSLICEINPUT DETECTORCutoff · SmoothingThresholdTRIG OUT 1ENV OUT 1OUTPUT DETECTORCutoff · SmoothingThresholdTRIG OUT 2ENV OUT 2
  • Close-up of Capicola's labeled controls and glowing amber LED rings
  • Capicola standing beside patch cables, with a second module in the rack behind it

Interactive manual

Play

Settings

Control

Pitch0 stStretch50%Threshold50%Grain Size1251Quality100%Feedback0Page / ResetSlice / SavePageIN LCV1CV3CV5OUT LIN RCV2CV4CV6OUT R

Performance Page

Primary

Pots
Pot 10 st
Pot 250%
Pot 350%
Pot 41251
Pot 5100%
Pot 60
Jacks
Jack 1Audio In
Jack 2Audio In
Jack 3Trig
Jack 4±5 V
Jack 5Trig
Jack 60–5 V
Jack 7Trig
Jack 80–5 V
Jack 9Audio Out
Jack 10Audio Out

Heavylight X Hermetic Modular

About Heavylight

Heavylight Industries started with a frustrated sampler user figuring out how to time stretch on a device that offered no such feature. The end result was the idea of non-uniform sampling: a novel, fast, keyframe-sampling compression and stretch algorithm.

Capicola is the first embodiment of this algorithm, but the "Keyframe" idea can power so much more: an endless CV recorder, a sampler, or maybe even an entirely new time-frequency representation for signals that will drive another dimension of audio possibilities. Only time will tell.

Matthew (Heavylight) and Luke (Hermetic), both residents of Cascadia, met by chance online. Hours after reaching out, the pair from the Pacific Northwest were hacking on the hardware prototype that was to become Capicola.

  • A hand holding Capicola with its illustrated panel fitted
  • Capicola running in a portable Eurorack case held in one hand

At a Glance

Specifications

Format
3U Eurorack
Width
12 HP
Depth
Skiff friendly
Power +12 V
<199 mA (LED-dependent)
Power −12 V
<50 mA
Audio
48 kHz / 24-bit stereo
CV jacks
6, field-programmable
LEDs
102 RGB
USB
Front-facing USB-C
Storage
Micro SD
Engine
Keyframe time-stretch
Pitch and time
Fully decoupled
Slicing
Per-channel transient detection
Modulation
Envelope followers, per pot
Feedback
0 to 2.0
Parameter lock
Every pot
Presets
16 slots

Open Platform

Use Any Alchemy Lab Firmware

Capicola is one firmware among many on the open Alchemy Lab platform. The hardware is field-programmable down to the silicon: load Echoa or Spagyros, build your own voice, or contribute back to the SDK. Capicola itself is open source, built on the Alchemy SDK.

License

MIT

HAL

Open

Panel templates

Included

Language

C++

Macro view of Alchemy Lab's exposed LED rings and control hardware
Capicola front panel with labeled controls, front viewCapicola front panel with silver illustration, reverse view
Reversible panel.Explore front panels →

Capicola

Slice and stretch in real time.

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