hyperSTACK – Polyphonic Chorus-based Software Subtractive Synthesizer

hyperSTACK is a polyphonic chorus-based software VST subtractive synthesizer. It is able to create a rich chorus effect by stacking up numerous oscillators, each with slightly different pitch, tone, and development. These oscillators are perceived as one single instrument with a “fat” sound, much like a choir or an ensemble of strings. Beware: this VST chews up your CPU!

This was my major project for COMP4121 ‘Advanced and Parallel Algorithms’ course at UNSW, 2010.
Screenshot of hyperSTACK user interface.

The main features of hyperSTACK:

  • Up to 64 polyphonic audio oscillators, available in fast low-quality mode or alias-free high-quality mode using the BLIT algorithm.
  • Sawtooth or Square waveforms.
  • Complete pitch vibrato engine, which is run individually for each oscillator;
    • Individual fast sine-estimation pitch modulation LFO for each oscillator.
    • LFOs controllable by ADSR envelope, to simulate violin vibrato coming in at the end of the note.
    • Variation from pitch modulation LFO using cosine interpolated Perlin noise functions, also controlled by the LFO ADSR envelope.
  • Chorus detune feature, which automatically evenly detunes every oscillator.
  • 8-voice MIDI polyphony.
  • Volume ADSR envelope, individual for each oscillator. The individual envelopes can be modulated via the Deviation knobs, which control how much each parameter evenly deviates from the mean. Resonating 24dB Butterworth Low-Pass filter, controllable by an ADSR envelope.

Audio Demo – MP3
VST Plugin Binaries – x86 Win32
VST Plugin Source – MSVS2005
User Manual
Source Code Reference

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