An LV2 synthesizer based on Triple Oscillator, a polyphonic subtractive synthesizer with three oscillators that can modulate each other in various ways.

Extends the original with several useful QOL features, including bandlimited synthesis by default, unison with many detuned voices, and legato.

Currently a work in progress, but usable nevertheless.

• 3 oscillators which can modulate eachother via phase, frequency, and amplitude modulation (PM, FM & AM) simultaneously
• Choose between 3 multimode filter models (RC, Ladder, Simper SVF) with keytracking and envelope
• Unlimited polyphony, with optional monophonic and legato modes
• ADSR envelopes with slopes smoothly adjustable from exponential to logarithmic.
• Sine, triangle, absolute sine, saw, and square waves
• Bandlimited wave synthesis using wavetables computed via FFT (harmonics extend up to the Nyquist frequency, with no unexpected drop-off)
• Detunable unison with (up to) 128 voices for each oscillator (i.e. yes it can supersaw)
• Integer frequency division/multiplication for each oscillator for harmonic sound effects
• Vibrato, tremolo and modulation control with an LFO
• Portamento and adjustable initial pitch slide for kickdrum synthesis.
• No GUI

Coming soon...

0. cd into the three_osc directory.
1. Run cargo build --release. This compiles the synth and updates the .ttl metadata in three_osc.lv2

2. Copy the built binary (./target/release/libthree_osc.so or libthree_osc.dll depending on your OS) into ./three_osc.lv2
3. Copy ./three_osc.lv2 into any of the default LV2 directories (e.g. YOUR_HOME_DIRECTORY/.lv2/).
4. Load it into your preferred LV2 host (Ardour, Carla, LMMS) and have fun.

2. Run copy_lv2.sh. This automatically does the manual instructions, copying ./three_osc.lv2 into your home YOUR_HOME_DIRECTORY/.lv2/ directory. Only works on linux because the script looks for libthree_osc.so, but should work on windows if you edit the script and change the copied file name to libthree_osc.dll.
3. Load it into your preferred LV2 host (Ardour, Carla, LMMS) and have fun.

• The absolute sine / exponential wave is like a saw wave where the harmonics decrease volume at -12dB per octave instead of -6 dB per octave (i.e. it's a saw wave tracked by a soft filter). Similarly, the triangle wave is like a square wave where the harmonics diminish at -12dB per octave instead of -6dB.
• Increasing envelope slope makes it steeper, decreasing it does the opposite. Slope = 0 gives perfectly linear slopes, which are not perceptually linear. Slope = 1 gives perceptually-linear (logarithmic) volume decay.
• The Ladder and RC filter models are both capable of self-resonance at resonance >= 9.0. Underdriving the filters (i.e. drive below 1) and sweeping them very slowly gives a 'harmonic snap' effect.
• Setting octave detune to -0.0028 gives near perfect fifths, while 0.0342 gives near perfect major thirds.
• FM changes frequency with the modulator's waveform, PM changes frequency with the derivative of the modulator's waveform. (I.E. PM by triangle == FM by square wave)

• I wanted to write a synthesiser.
• I'm currently migrating from LMMS to Ardour. Surge and ZynAddSubFx are great synths, but...
  • Controls are spread out over multiple tabs / screens.
  • Surge is a little bit aggressive.
  • Sometimes you want to quickly make simple and predictable sounds.
• The original Triple Oscillator mostly solves these problems, but has issues of its own:
  • LMMS exclusive.
  • A bit loud.
  • Volume envelope is optional.
  • No phase randomness.
  • Originally had no bandlimited wave generation.

• Stereo
• Use naive wave generation for modulation between oscillators? (stop ringing artifacts)
• Add oversampling with a control (for FM / PM)
• Switch between Naive, Wavetable, and Additive synthesis with a control
• Only generate unique wavetables when necessary (i.e. every third note, and only when harmonic count changes)
• Adjust more knobs to sensible values / defaults
• Add presets that make the synth look good (current idea: reimplement/extend patches from MDA jx10, which are unreasonably nice)
• Make the build system nicer
• Tools for working with the harmonic series
• Use audio buffering for more optimisations
• Optimise
• Extract DSP to internal crate
• Port to https://github.com/robbert-vdh/nih-plug
• Sinc interpolation for wavetables instead of Lerp
• SIMD accelerate stereo paths
• Approximate/cache expensive computations (i.e. any uses of powf)
• Fix buffer size to reduce expensive modulation calculations at the expense of sample-accurate automation (make const so that you can play around with buffer lengths, see what is good)
• Add midi pitch bend support
• Come up with better name for "Initial Pitch Slide" control
• Add UI using nih-plug, make it functional
  • 1 page, all controls
  • 2nd page for oversampling and other unimportant things
• Load Scala .scl and .kbm files
• Publish

The Three Osc project is licensed under the GNU General Public Licence version 3.