I’m looking for some new sounds and techniques for VCV Rack, and something I want to experiment with is to create sustained, dense, random percussive textures, similar to what a percussionist might create with rattles, rainsticks, found percussion sources, etc.
An example:
The quick minimum-viable approach I can think of off the top of my head would be to ping a bunch of bandpass filters while randomly modulating cutoff and other params, followed by some additional processing to shape the sound… But this feels way too rudimentary and there must be more efficient and better sounding approaches. Maybe granular synthesis?
That’s a challenge…especially getting density right.
A physical modeling approach (Exciter/Resonator combo’s) could be a good start for this. Exciters could be all sorts of sources of clicks, pulses or (filtered/shaped noise) bursts. Resonators could be Modal nodes, Resonant filters and such. Or Feedback Delay line based (e.g. Karplus Strong like Waveguide structures) or Comb Filters.
Also, FM/PM might be a viable option for these not-to-complex and short percussive sounds. This more or less implies triggering individual sounds with more control over spectrum and timing via triggers/envelopes/modulation.
Also, consider Additive for these sparse spectra. Especially check out docBOscA1 which offers a great additive + comb filter approach.
Noise pulses might be the way to go for some of these sounds.
Granular can also give you control over density, but maybe not so much over (individual) triggers, envelopes and pitches.
Generally, the higher (and shorter) the individual ‘notes’, the less relevant the actual spectrum will become. At some point, just bare sines will even do.
Just had a short try for the rattles in the example video, using FM. since that would give me the most control I guess.
Tiny TricksSample and hold x16 triggered by Binary noise into VCVMerge into VCVVCA to generate several channels of random voltage within a controllable amplitude range, add VCVCV Mix or some offset/scale tool were needed keep modulation above/within some desired voltages.
Two BogaudioFM-OP to actually create the single percussive/rattle sounds. Modulator at full sustain/level, used to emulated some resonant frequency(band). Carrier using built-in enevlope with short decay/release. Generally, tune modulator and carrier from the same source and (de)tune them relative to each other as needed. But even a single FM OP (with some feedback) can yield OK results with these relatively high pitches and fast decay/release times.
Trigger the carrier gate with the random pulses from the Out of Binary noise (using Sample Rate and Probability to set the ‘pattern’).
Modulate FM amount and/or V/oct using the random voltages, so all individual sounds are a bit different. Same for amplitide/level.
Finally feed that through a resonant High Pass or Band Pass Filter.
This very basic setup generates somewhat credible sustaining rattle sounds as in the example video. Adding some overall envelope for density of trigger pattern and amplitude might give the effect of brushing the rattle. As expected, getting trigger speeds and intervals right is somewhat tricky. But, these ideas might be a usefull starting point.
Hora Soft Bell makes a nice clave. Get the triggers right and you have a rattle.
Easiest way to get triggers is 4ms SCM. Use all the outputs from SCM, each driving its own clave. The more you modulate SCM, the more chaotic the trigger patterns.
Interesting topic, try this module for triggers. It’s described as a ‘physics based shaker’.
Plaits has some models which are useful for this too, such as particle noise.
Also, try pinging filters or resonators but patch the impulse noise through delays first. That makes some interesting and more organic sounds.
Physical Modeling is generally about Exciters and Resonators. Exciters can be any audiosignal (from short pulses to longer enveloped or sustained sounds). The harder part is the Resonator behaviour.
There are several explicit Physical Modeling options in VCV Rack. Mostly focused on offering the Resonator functionality. Some incorporate Exciters and can be triggered. Most offer an Audio IN for an Exciter signal.
Some great Physical Modeling modules, like the Saphire modules are less fitting for the purpose of the emulation of sustained rattle-like stochastic percussive sounds.
Generally I’d focus on the more modules/generic techniques
Delay/Feedback/WaveGuide based (Karplus-Strong, basic Waveguides)
Resonant Filter based (e.g. Narrow High Rez Bandpass, Modal).
Comb Filter w/feedback based
Obviously there are the obiquitous Mutable Instruments derived multi-model Modules (including various Firmware alternatives)
Several general purpose HPF, BPF, LPF filters also have great (high) resonance characters. Many are also pretty good at following V/Oct. Filters are also very usefull in shaping an Exciter signals.
Creating a feedback loop around filters or filter banks (including EQ’s) is also an option. A EQ/filterbank like BogaudioPEQ, BogaudioPEQ6, BogaudioPEQ14 can even follow V/Oct.
Any fast enough delay can be used for Karplus Strong / Waveguide like effects. But not all are (simply) V/Oct tunable. Lengthening the delayline will lower its frequency and detune the construct (e.g. by incorporating other modules like filters or non-linear transformers/waveshapers using cables which each add a sample delay…and possibly their own resonance). You will need to compensate with sample delay(s). Any introduction of DC offset accumulates in a feedback loop.
Also, positive feedback will maintain the full spectrum (for vibrating snares and such). Negative (inverted) feedback will (or might) drop the frequency of the delay line by an octave and cancel out even harmonics (leaving the 'hollower’odds for flutes and such).
O, and any feedback based construct might suddenly spiral out of control, so protect ears and gears.
