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∞Open Rack · polyphonic synth

Helm synth

The sound engine of Helm, an open-source subtractive synthesizer, running in your browser. Two oscillators with unison, a sub and noise, a resonant filter, three envelopes, LFOs, an arpeggiator, a step sequencer and effects. The panel is our own; every patch here is free to share ({{PATCH_COUNT}} in all).

Loads about {{DL_KB}} KB the first time.

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Choose a patch

C3

Computer keys: A W S E D F T G Y H U J K play notes, Z / X change octave. Tap a key nearer the bottom to play it louder. Double-click a slider to reset it.

About this page

What's here

  • Helm's synthesis engine (the mopo DSP library and Helm's voice, filter, envelope, LFO, arpeggiator, step sequencer and effects code), compiled to WebAssembly from the GPL-3.0-or-later source.
  • {{GPL_COUNT}} patches from Helm's own collection that their author released under GPL-3.0-or-later. They were saved by an older Helm version and are converted the same way Helm itself converts them.
  • {{CC0_COUNT}} new patches made for ∞Open Rack, released as CC0 (public domain).
  • A new interface, drawn for ∞Open Rack. Helm's own interface and artwork are not used.

Left out on purpose

  • {{EXCLUDED_COUNT}} factory presets that are licensed CC BY 4.0. This page only ships patches that are GPL or CC0.
  • The plugin's own interface, skins, fonts and graphics, and the JUCE framework it uses (not needed in the browser).
  • Saving patches: edits last until you change patch or reload the page.

Sound runs on a separate audio thread in your browser. Nothing you play is recorded or sent anywhere.

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