How to bring physical modelling into your synthesizer
First of all, what is physical modelling?
“Physical modelling synthesis refers to sound synthesis methods in which the waveform of the sound to be generated is computed using a mathematical model, a set of equations and algorithms to simulate a physical source of sound, usually a musical instrument.” Wikipedia
To mimic acoustic musical instruments within a modular synthesizer is a special challenge. Nonetheless, there are some modules that accept this challenge and bring physical modelling to eurorack. As the computing power is increasing steadily it is no surprise that manufacturers started developing more complex digital voice modules. These modules can do things that only plugins could do a few years back, but now with CV controllable parameters.
What choices do you have in eurorack?
One of the most recent developments is the Intellijel Plonk. This module takes all the advantages of modern computing on small space and adds a nice OLED screen for operating the numerous possibilities the module gives you. Plonk is the result of a collaboration between Intellijel and Applied Acoustics Systems (AAS). It features two virtual exciters, which can be used individually or in combination. The first one is a mallet simulation with variable stiffness. The other exciter is a white noise source with variable clock rate. Its signals can be shaped via a low-pass, a high-pass filter plus an AD respectively AHD envelope. The resonator can be a string, one of two blocks, a circular respectively rectangular membrane or a plate. Its properties are definable via decay, tone and inharmonicity parameters, a high pass filter plus a pitch envelope. As a result, it is possible to simulate materials like wood, metal or plastic. Furthermore, users can determine where the exciter signal is applied to the resonator.
Elements & Rings
Two modules, that set the bar for physical modelling in eurorack – at the time they were released, are Elements and Rings by Mutable Instruments. Elements features two separate sections, on the left side you can find the exciter and on the right side the resonator. Elements is based on modal synthesis, an under-appreciated form of physical modeling. It combines an exciter synthesis section for raw and noise sounds with the characteristics of a bowed, blown or struck instrument with a modal filter bank consisting of 64 tuned band pass filters. This filter bank simulates the behavior of resonant structures. Brightness and damping can be adjusted and a stereo reverb adds room to the sound. One interesting thing about Elements is that you can use the resonator part independently, so you basically can use any signal as an exciter.
Rings is somehow based on the resonator part of Elements, with some adjustments, updated features and a four voice fake-polyphony. Two outputs are available, each playing different harmonic structures or different notes in polyphonic mode. As expected from a resonator it is possible to process audio signals but Rings can also be played exclusively via CVs as it can excite and play sounds by itself. Sound wise there is more than just nylon string imitation but singing tones, cold strings and also very experimental and extreme sounds.
At this point we have already captured the most versatile physical modelling modules available for eurorack. But there are some more that focus on a special variety of physical modelling: Karplus Strong Synthesis.
The Proton is Audio Damages take on this interesting synthesis method. The digital module offers a tuned delay line with very short time settings – a basic requirement for Karplus Strong. A noise burst impulse excites the delay core and can be shaped for different sonic results, especially when combined with open damping it produces interesting noisy, metallic sounds. Karplus-Strong loses amplitude in the low frequency range for which reason Proton features SUB, a sine wave tuned to the fundamental which can be mixed with the physical modeling sound. The audio input makes it possible to use the module as a digital delay or to mix the generated sound with external.
Another Karplus Strong module is the CG Products Delay1022 Mk2 – the only full analogue module in this list. The 1022 is a very clear and short delay module, it can delay in audio rate and at high feedback setting it provides very interesting sound sculpting possibilities. The module is perfectly suited for Karplus-Strong synthesis. The 1022 can process external audio or be fed with just a trigger, then it will create percussive plucked sounds, strings and drums at high feedback settings. The delay time controls the frequency, feedback amount controls decay time. A highly recommended module with a unique deep sound.
And there is the Make Noise Mysteron. A digital waveguide synthesis module. …yes me too, I don’t know what this is. And the people at Make Noise are so kind, to not leave us alone with this feeling: “The Mysteron is a voltage controlled Dual Digital Waveguide algorithm that is a bit of a mystery even to those of us involved in its design.” (makenoisemusic.com)
But it sounds great, so why bother. The Mysteron is a unique module and pushes the sonic boundaries of modular synthesizers even further.
This is by no means a complete overview of available modules nor a full review of the discussed modules. The what about… text are here to give you new ideas and maybe another perspective on things. All these modules offer more features than we have talked about in this post. For further information please click the provided links or – even better – visit the shop and ask the SchneidersLaden experts in the showroom.