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KVR Developer Challenge 2023KVRDC23: Acousmodules SpatStrument SM24 - Free Spatial Audio Synthesizer and Sampler Plugin for macOS & Windows, VST3


The KVR Developer Challenge 2023 is now at the download and voting stage it's time to focus on each of the 23 entries that are available now, for free, for everyone.

SpatStrument SM24 by Acousmodules
macOS & Windows, VST3

It's not an effect, it's not a synthesizer, it's not a sampler, it's not a 3D panner, it's not a controller... but it is all of this: it is the SpatStrument SM24.

Spatialization of sound with "3D panner" type tools is now a common and easy thing, and the popularization of spatial audio with Dolby Atmos and ambisonic technique makes it almost fashionable. But considering a loudspeaker space as a concrete dimension of sound which can be modeled in a global way still remains the task of kind of "hackers", most often requiring specialized and somewhat complex environments.

Thanks to the recent expansion of MPE gesture controllers (my first one was the LinnStrument...), this SpatStrument should make it possible to approach audio-spatial sculpting in a playful and creative way, whether it is done inside standardized broadcast formats or in the freedom of original creations.

This plugin may interest firstly people who play electronic and electroacoustic live music, but also those who compose in multichannel studios to create fixed media works for domes, cinema / Dolby Atmos, acousmoniums or whatever they like, with ambisonics or even binaural with the appropriate convertors.

Fortunately, it can also work in stereo with an ordinary keyboard to be able to rave a little with the sounds in the absence of their space.


  • Up to 24 output channels with totally free speakers arrangement in 2D or 3D space.
  • Mono audio input for live processing and realtime sampling.
  • Periphonic Spatial Mode to simplify the use with surround / immersive common formats (domes, Atmos 7.1.4, 9.1.6, 11.1.8, NHK 22.2...).
  • Volumetric Spatial Mode for advanced spatial creation and true 3D speakers arrangements like 4DSound.
  • 8 MPE polyphony voices.
  • Direct spatialization of the 8 polyphony voices with 8 independent 3 dimensional fingertips.
  • Shapes based spatial synthesis (Rings, Lines, Cube, Chaos) that can be combined and animated with different modulators and synchronized with sampling and synthesis parameters.
  • No including ambisonics and binaural processing, but just use the ones you prefer. IEM and SPARTA are free and among the bests, and special configuration files are provided for these tools...
  • Can also work in stereo;-).
  • Input Live processing: play a hardware or software instrument through it to add spatialization and effects, together with additional filter and envelope; spatialize a track content with a MPE controller; use the audio input level to modulate sound and space parameters (Envelope Follower).
  • Ring Modulation between the Live Input and the Sampler or the Synthesis.
  • Sampler: sample the audio Input or load an audio file; play it through a multimode filter, with its ADSR and LFO; control the Start and Loop points of the 8 polyphony voices independently with the fingers.
  • Synthesizer: 3 oscillators subtractive principle with FM, Synchro, multimode Filter and wide range ADSR and LFO modulations (it may not be well suited to play scaled melodies...).
  • MPE MOD: use the X, Y, Z fingers positions, their distance and angle from the center to modulate every sampler and synthesizer parameters polyphonically.
  • Cross Modulation between the sampling and the synthesis sections.
  • Octo FX: 8 channels Delay/Resonator and Hall Reverberation (Freeverb in Mac version).
  • Alternative Triggers (Windows only): AutoTrigger and VeloPad, for granular like effects (experimental...); the VeloPad can send MIDI Notes to other devices if the host allows it.
  • All parameters in one screen: What You See Is What You Generate.


A VST3 host that can use multichannel plugins.

The ideal is to have multichannel busses (multitrack DAWs: Reaper, Ardour, Pyramix...) or to allow to connect freely the inputs and outputs (modular hosts: Bidule, Usine Hollyhock, Element, Max/Msp...), but some stereo only DAWs can nevertheless distribute a series of outputs on several stereo busses (Live, FLStudio, Waveform ...), or at least accept to use only the two first is you play in stereo.
Note that it will not work in Steinberg's products.

Optional but highly desirable, an MPE controller with enough physical space, sensitivity and accuracy for XYZ fingers movements (Sensel Morph, Push 3...).

The SpatStrument is made with the 1.5 beta version of SynthEdit, and uses also the beta version of Elena Design's sampling framework, without whom this plugin could not exist.

User Guide, Presets, additional files and video tutorials are available on the site page, and will be regularly updated: acousmodules.free.fr/spatstrument.htm

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