This Month’s Module: Add Movement to Your Eurorack Patches with Frap Tools Falistri
In a Eurorack modular system, Falistri is most useful as a pair of flexible modulation sources, though its capabilities go far beyond.
Frap Tools calls Falistri a Movement Manager. It builds on the concept of the classic Buchla 281 Quad Function Generator, but with some significant enhancements. It is a multifunction module, with the green and yellow graphics identifying the two function generators at its core. The gray, red, and blue sections respectively indicate an additional pair of clock dividers, a four-quadrant multiplier, and a slew generator. These graphics consist almost entirely of symbols rather than words, making Frap Tools’ modules a bit cryptic at first glance. Nonetheless, they’re quite logical once you spend time learning their system.
Rise, Fall, and Shape
You can trigger each function generator via large front panel buttons. Nearby arrows point to the jacks where you can patch in external trigger and gate signals. A switch chooses between Transient (Rise/Fall), Sustained (Rise/Sustain/Fall), and Loop (LFO) modes. A second gate input near this switch enables Loop mode just while the gate is high, creating vibrato-style effects that fade in and out per note event.
The large knobs down the center of the module set the rise and fall times for each generator. When the Time Scale switches along the left edge are in their slow position, these times can range from under a millisecond to over 8 seconds. Setting Time Scale to fast optimizes that function generator for audio-rate oscillations and envelope blips. The latter is useful when an oscillator triggers it, creating formant-style waveforms in response.
Dotted lines connect the Rise and Fall knobs to a pair of jacks that provide voltage control over their times. A positive voltage at these is the equivalent of turning the knob clockwise, lengthening the time. For example, if you patch a velocity control voltage to these, higher velocity values will create longer notes—akin to striking an acoustic object harder.
A third jack is connected graphically through a musical note icon to the normal time CV jacks. This jack controls both Rise and Fall with the opposite effect: higher voltages are the equivalent of turning both knobs counterclockwise for shorter times. This is where you patch a 1-volt-per-octave keyboard control voltage, as higher voltages require shorter oscillation periods to create higher-pitched notes. I also found this useful with the envelope modes, as higher notes will then result in faster envelopes, mimicking the behavior of acoustic instruments such as the piano.
There are also Shape controls for each stage, covering logarithmic through linear to exponential. Falistri places the shape circuitry after the rise/fall circuitry, meaning its oscillation or envelope rates stay the same regardless of the shape you choose. This is an advantage over the multitude of envelope generators where changing their shape also changes their time. This is particularly handy in VCO mode.
Outputs and Interactions
The output section for each function generator is equally versatile. Two dots next to a jack indicate a bipolar output, with a voltage range of ±5 volts. One dot indicates a unipolar output, with a range of 0–10 volts. Adjacent to these are a pair of “end of stage” gate signals. EOR goes high when the Rise stage has finished, and low when the Fall stage has finished; EOF goes high when the Fall stage has finished, and low when the Rise stage begins.
Each generator also has an attenuverter (an attenuator that can also invert a signal) with its own output jack. The attenuverted outputs for each function generator are internally patched to a “max” or “analog OR” section, which passes the higher of the two voltages to its own jack. This is a great way to combine two simultaneous envelopes or LFOs into a more complex shape without the need for an external mixer.
To the right of the max output jack is a switch labeled Q. This puts Falistri into Quadrature mode, where the end-of-stage signals for each generator triggers the next stage in the other generator. This is a case where you want to study the pleasantly thorough online manual to fully understand how these parts interact.
When set to Loop mode with Time Scale set to fast, Falistri’s function generators become VCOs that can track a 1-volt-per-octave signal accurately over several octaves. The secret is that the Rise and Fall times must be set identically. If greater the difference between the Rise and Fall times, the less accurately it tracks.
This means Falistri is essentially a triangle-wave oscillator. However, you can use the manual Shape controls to alter the harmonic content. Also, Falistri’s utility sections include octave dividers and a ring modulator, further increasing its tonal range.
As I mentioned earlier, Falistri offers three additional utility sections. They may be patched externally for use with other modules; some also have inputs normalized to the two internal function generators.
The gray section is a pair of “flip-flops” that alternate their outputs between high and low voltages for each new rising edge at their inputs. These can be used as clock dividers or sub-octave generators. Again, two dots next to a jack indicates a bipolar output; one dot indicates a unipolar output.
The blue section is a linear slew generator, with separate Rise and Fall times. The yellow function generator’s unipolar output is normalized to its input. I’ve used this to smooth out fast envelopes or jagged LFO shapes to create a second, related-but-different output from a single generator.
The red section is a four-quadrant multiplier (also known as a ring modulator), which multiplies together the levels of the voltages at its two inputs to create a new output. Its inputs are normalized to the yellow generator’s unipolar output and the green generator’s bipolar output. With this default patch, the yellow generator controls the green generator’s output level, fading it in and out over time.
However, if you patch the yellow generator’s bipolar output to the multiplier’s first input, you then get a more complex output, in which a negative voltage from the yellow side flips the polarity of the green section’s signal. This is a great way to combine LFOs to create a far more complex pattern. If you are using Falistri as a pair of VCOs, this multiplier section acts as an amplitude or ring modulator, depending on how you have it patched.
Overall, Frap Tools modules are generally not small, inexpensive, or blindingly obvious to use. But once you get into them, you will find they are very logical, and they provide a lot of extended functionality. Falistri is no exception.
Synth and Software thanks longtime modular user and former synth designer Chris Meyer for his contribution. Chris is the force behind Learning Modular, where he teaches others how to master modular synthesis.
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