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10 Voice Polyphonic Virtual Analogue Synthesiser

(5 Votes)
Ev Buckley
1.0 (Updated 11 months ago)
October 11, 2021
Reaktor 6


SeerX is a 10 voice polyphonic virtual analogue synthesiser, with dual oscillators, dual filters, dual envelopes, independent saturation, and both polyphonic and monophonic modulation.

All Reaktor programming, panel design, and presets are by Ev Buckley.


SeerX provides two oscillators. Oscillator 1 is a Square/Saw oscillator with pulse width, amplitude, and frequency modulation, and Oscillator 2 is a Saw/Pulse/Triangle oscillator with oscillator sync, pulse width modulation and a pitch offset control. The second oscillator operates as the frequency and amplitude modulation source for the first. There is also a sub oscillator that gives a sine wave at one octave below Oscillator 1, and a noise source. Coarse tuning is +/- one octave, and fine tuning is +/- 1 semitone.


The saturator follows the oscillator section directly. It gives 2x oversampled saturation controlled by a pre-saturation gain control, with a trim control after the saturator to manage levels entering the filter. The input provides enough gain to saturate the sub oscillator into an approximate square wave. The oversampling process is taken from the SKF Reaktor Block.

Dual Filters:

The filter section of SeerX is a dual multimode design offering two individual filters switchable between 12dB Low Pass, 12dB High Pass, or 6dB Band Pass operation. The filters can be arranged in parallel or serially, and their controls can be operated independently or linked. In linked operation both filter controls override one another, so that moving either cutoff or resonance control sets both filters to that value. Filter Type selection remains independent.

Both filter cutoffs are modulated by the Filter Envelope, the Mod Wheel modulator, and the Polyphonic Modulation bus, as well as by a To Filter control from the Amplitude Envelope. The Amplitude and Filter envelopes affect both cutoff frequencies equally, and the Wheel and Polyphonic modulations can be assigned to one or both filters independently.


There are two modulation sources in SeerX, one monophonic source controlled by the modulation wheel of a keyboard controller or other MIDI source that applies to all voices collectively, and one polyphonic source that applies to each voice individually.

The monophonic Wheel Mod blends an LFO with a noise source, applies an amplification scale, and passes the result to the Oscillator frequencies and pulse widths, and the Filter cutoffs. The LFO has Triangle, Saw, and Square waveforms, and can be smoothed to shape the waveforms further.

The Polyphonic Modulation section mixes the Filter Envelope with the output of Oscillator 2 and sends the result to the frequency of Oscillator 1 for FM synthesis, the amplitude of Oscillator 1 for AM synthesis, the pulse width of either Oscillator, or the frequencies of either Filter cutoff. This modulator is polyphonic, so each voice reacts independently to its own envelope triggers and oscillator frequencies.

Master Section:

After the tone generation and shaping, SeerX has a simple delay processor with 1 second of delay time and feedback, followed by a one-knob compressor to add further warmth and tame sudden level spikes caused by polyphonic playing. The entire synthesiser architecture is mono from start to finish.

SeerX comes with a dozen basic example programs embedded in the instrument file.

If you like SeerX and want to support me in creating it and other Reaktor software, you can donate via PayPal here:

Any contribution at all is greatly appreciated but if you are not in a position to support, please use and share SeerX as much as you like, regardless.


Diego deus
5 months ago
A lot of thanks! Thank you!
Ev Buckley
11 months ago
Thank you bindlestiff! I'm delighted to know you're inspired by SeerX, it makes building it worthwhile :)
11 months ago
Nice! There's a great variety of sonic potential from the dozen basic presets provided, thanks to the onboard filter and mod sections. Been pulling lovely sounds out of this since it was launched. Thanks!
Ev Buckley
11 months ago
Thanks, Jonathan! It was refreshing to build a ten-fingers-on-the-keyboard instrument, when so much of my work is about knob twiddling :)
Jonathan Tremblay
11 months ago