A free and open source frequency modulation-based synthesizer plugin. Runs on macOS, Windows and Linux in VST2-compatible hosts.

Latest release

OctaSine v0.7.0

2022-06-08 - Release notes

After downloading the archive, unzip it and move OctaSine 0.7.vst to your VST2 plugin directory. Typically, it is /Library/Audio/Plug-Ins/VST/.

You might need to allow MacOS to open applications from any developer. To do this, open a terminal window, enter sudo spctl --master-disable, press enter, enter your password and press enter again. More info here.

Distributed under the AGPLv3 license.

After downloading the archive, unzip it and move OctaSine 0.7.dll to your VST2 plugin directory. The standard locations are:

C:\Program Files\VSTPlugins or
C:\Program Files\Steinberg\VSTPlugins or
C:\Program Files\Common Files\VST2 or
C:\Program Files\Common Files\Steinberg\VST2

Distributed under the AGPLv3 license.

After downloading the archive, unzip it and move OctaSine 0.7.so to your VST2 plugin directory.

There is also the option of building OctaSine from source.

Distributed under the AGPLv3 license.

OctaSine screeshot


Four operators

Four FM operators with parameters for volume, panning, feedback, frequency modifiers (ratio, free and fine), envelope values (attack, decay, sustain, release) and toggling of white noise mode.

Flexible routing

Flexible routing allows setting the operator modulation targets (with some limitations) as well as the amount of signal that is simply added to the final output, enabling additive synthesis.

Four LFOs

Four LFOs with multiple waveforms, oneshot and loop modes and optional DAW BPM sync. They can target most operator parameters and most parameters of lower-index LFOs.

ADSR envelopes

Each operator is connected to an attack-decay-sustain-release volume envelope with logarithmic slopes.

White noise mode

Per-operator white noise mode makes it easy to create percussive sounds such as hi-hats and cymbals.


Runs on macOS, Windows 10 and Linux (X11) in VST2-compatible DAWs on 64-bit computers. Synthesis is SIMD-accelerated on x86_64.

Audio samples

Frequently asked questions

How do I suggest improvements or report a bug?

If you want to suggest improvements or report a bug, please open an issue. To do this, you need to create a GitHub account. It is easier than it sounds - you only need an email address and a password.

If you're reporting a bug, please use the "Bug report" template.

How do I export and import patches?

Please use the functionality provided by your DAW for exporting/importing .fxp/.fxb files.

Ableton Live
Use the disk icon to save individual patches or the whole bank. Use the folder icon to select and load previously saved patches or patch banks.
Use Export VST patch/bank file (.fxp/.fxb)

There are audio artifacts when using OctaSine with FL Studio!

Please upgrade to version 0.6.0 or later. If you want to keep using an older version, please enable the following FL Studio audio processing options:

  • Use fixed size buffers
  • Process maximum size buffers

Why is the plugin called OctaSine?

The name OctaSine comes from the four stereo sine-wave operators. Frequency modulation is done twice per operator, enabling modulation panning.