Unleashing Sonic Transformations: Exploring the Morphing Filter Bank

As an evolution in formant filtering, the Morphing Filter Bank takes a unique approach that's not seen very often. The module is based upon four fixed frequency resonant bandpass filters that are intertwined in a feedback loop. By regulating the gain of this feedback loop through the voice control, the resonant peak of each filter splits into two distinct peaks, which then diverge across the audio frequency spectrum. This divergence can add striking vocalizations to sound patches or perhaps subtle shifts in timbre, offering a palette of sound design options to the user.

In addition to the bandpass outputs, we also have a variable notch output. At zero level voice control, the frequency response of the variable notch output stays flat, letting all the frequencies pass unaltered. Modulating the voice control hones the notch’s width and depth, introducing a phaser-like sound along with the formant filtering. Because a notch filter allows both high and low frequencies to pass, it is exceptional for adding dynamism to bass patches.

The Morphing Filter Bank is a part of a limited release series, hand-assembled and rigorously tested in Brooklyn, New York. The audio signal path integrates high-quality, hand-matched film capacitors contributing to the purity of the sound.

One of the most intriguing aspects of the Morphing Filter Bank is its availability in two different versions: OTA and Vactrol. The OTA or Operational Transconductance Amplifier variant is responsive to incoming control voltage (CV), delivering superior performance with audio rate modulation. Moreover, the OTA adds a distinctive character to what would otherwise be a rather clean filter seeing how OTAs are known for their distinct character.

The Vactrol variant, on the other hand, offers a slower responsivity to the incoming CV, resulting in a cleaner filter sound, and is capable of achieving deeper levels of modulation. It can even drive the bandpass filters into self-oscillation with the correct adjustment of the PCB's trimmer.

To summarize, the Morphing Filter Bank presents a unique take on formant filtering, providing versatile capabilities from vocalizations to subtle timbral shifts and bass motion. Whether you want to enrich your patches with vocal-like character or intricate, phaser-like motions, the Morphing Filter Bank certainly broadens your sonic canvas. Its potential for creating complex resonant peaks and their consequent divergences across the frequency spectrum, coupled with the choice between OTA and Vactrol versions, makes this module an exceptional tool in modular synthesis and, more broadly, the realm of sound design.

Example Usage

Novice-level usage example:

To start exploring the possibilities of the Morphing Filter Bank, let's create a patch that adds some vocal-like qualities to a synthesizer sound.

First, connect the output of your oscillator module to the input of the Morphing Filter Bank. You can use any oscillator you like, such as a basic sawtooth wave.

Next, let's focus on the bandpass outputs of the filter bank. Connect one of the bandpass outputs, let's say the second one, to a mixer or VCA module for further processing. Adjust the cutoff frequency of this bandpass filter to a value that you find pleasing, emphasizing a specific range of frequencies.

Now, let's add some movement to the sound. Connect a low-frequency oscillator (LFO) module, such as a square wave LFO, to the voice control input of the Morphing Filter Bank. This will modulate the gain of the feedback loop and cause the peaks of the bandpass filter to split and move around. Start with a slow modulation rate to hear the gradual changes.

Play around with the depth of modulation by adjusting the LFO's amplitude. This will determine how much the filter peaks diverge and create interesting formant-like changes. Experiment with different modulation rates to find the right amount of movement for your sound.

If you want to add more depth and complexity to the sound, try using the variable notch output. Connect it to another mixer or VCA module. When the notch output is at its neutral position, it allows all frequencies to pass unaltered. But by modulating the voice control input, you can widen and deepen the notch, creating a phaser-like effect coupled with the formant filtering. This can be particularly effective for adding motion to bass patches.

Remember to experiment and trust your ears. Explore different combinations of oscillator waveforms, cutoff frequencies, modulation rates, and depth to create unique sonic transformations with the Morphing Filter Bank. Have fun experimenting and discovering new sounds!

Usage Example:

To demonstrate the versatility of the Morphing Filter Bank, let's explore an intermediate-level patch that adds subtle timbral shifts to a melodic sequence.

First, let's create a simple sequence using a Eurorack sequencer and an oscillator of your choice. Connect the audio output of the oscillator to the input of the Morphing Filter Bank.

Next, we'll set up modulation sources for the Morphing Filter Bank. Patch an LFO into the voice control input to modulate the gain of the feedback loop. Adjust the LFO rate to a slow and smooth setting to achieve gradual morphing effects.

Now, for the output, let's use one of the bandpass outputs and the variable notch output simultaneously. Patch the bandpass output to a mixer or VCA to control the intensity of the filtered sound. Connect the variable notch output to another input on the mixer or VCA.

To add dynamic movement to the patch, use an envelope generator patched into the VCA controlling the variable notch output. Adjust the envelope's attack, decay, and release settings to shape the motion of the notch filter's width and depth.

Play back your sequence and gradually increase the modulation depth and rate of the Morphing Filter Bank. Observe how the resonant peaks of the bandpass filters split and diverge, adding subtle yet engaging changes to the timbre of your sound.

Experiment with different LFO shapes, envelope settings, and voltage sources to further explore the sonic possibilities of the Morphing Filter Bank. Don't be afraid to push the module to its limits and discover unique sound transformations.

Further Thoughts

Imagine having a rhythmic drum sequence that needs some extra movement and character. By integrating the shkrjn Morphing Filter Bank into your modular setup, you can unlock a world of sonic transformations for your beats.

Start by patching a clock signal into the voice control input of the module. Adjust the voice control knob to a moderate position where it will provide a noticeable effect on the filter's behavior. Now, connect the drum sequence to the audio input of the Morphing Filter Bank.

Next, take the bandpass outputs of the module and route them individually to different destinations in your modular system. For example, you can patch one bandpass output to a VCA controlling the amplitude of a snappy percussive sound, while another bandpass output enhances the tonality of a melodic synth line. Feel free to experiment with different connections and destinations to explore the full potential of the Morphing Filter Bank.

To add even more depth and movement to your drum sequence, utilize the variable notch output. Patch it to a low-frequency oscillator (LFO) or an envelope generator modulating the cutoff frequency of another filter in your system. This will create a swirling phaser-like effect that adds an extra layer of motion to your bass patches.

Additionally, take advantage of the two available versions of the Morphing Filter Bank. If you crave instant response and want to push the filter into audio-rate modulation, opt for the OTA variant. Its fast response will provide a snappy and dynamic performance. On the other hand, if you desire a cleaner sound with deeper levels of modulation, the Vactrol variant is the perfect choice. Experiment with both versions to find the one that best suits your sonic preferences.

With the Morphing Filter Bank as part of your modular arsenal, you can elevate your drum sequences from simple rhythms to intricate sonic journeys. Unleash the power of formant filtering and transform your beats into captivating soundscapes.