The Krell patch is Todd Barton’s modular interpretation of the Ancient Music of Krell song from the 1956 Forbidden Planet film soundtrack.1
When it emerges from the skronky murk, the Krell is a writhing, cavorting phantasm. The challenge with Krell is to find a combination of settings and routings that brings out the soul in the machine. The basic idea is simple enough, but the details and subtle modulation are where it comes alive.
At the heart of it is a single looping envelope controlling a master output VCA with seperate modulations for the attack and fall portions the envelope. These rise and fall modulations can give amazing variations in tempo and dynamics depending on how the modulations are applied. Set the envelope to have a short attack and decay phase. An AD envelope that has an end-of-cycle (EOC) gate output and rise and fall modulation control is ideal. The cycling EOC gate trigger drives the entire patch. Use the EOC gate to grab a random pitch voltage and feed it to the VCO controlled by the master output VCA. Use slow random VCO FM modulations to make the patch breathe. A final random modulated filter adds timbral variation.
When it emerges from the skronky murk, the Krell is a writhing, cavorting phantasm.
A module that provides some level of control over a random voltage is pretty essential for Krell. However, you can get pretty far with some sample and hold, slew, mixers, VCAs, and noise/LFOs. At each point along the relatively simple path outlined below, you can add as much or as little modulation as the patch needs, or your system can provide. Remember to use VCAs to control the various random modulations.
In a Buchla system, a Source of Uncertainty module would be the optimal way to provide the controlled randomness that drives the VCO pitch, timbre and other random elements of the patch. Just substitute whatever random voltages you have at hand. The more closely you can relate these voltages to each other, the more dynamic your Krell will sound. Add correlation between elements such as pitch, FM depth and filter frequency to really make this patch sing. For example, use one related random voltage to generate pitch, and the other to sweep the filter frequency. Modulate the attack and decay parameters of the master envelope with cross patched LFOs. Firing everything with the EOC gate will keep all the various parts of the patch in sync.
There is any number of variations of this patch and it can grow and be expanded upon to fit whatever size modular system you have at hand. Start simple. Get to know the beast. A post by user Fhars on muff-wiggler is also particularly illuminating in translating the patch for eurorack2.
Simplifed Krell patch