Audio plug-in support

Audio plugins

Drop a plug-in from the Audio section of the process library into an interval or the graph. Cable audio, MIDI and control ports according to the plug-in’s declared inputs and outputs.

If the plug-in has a custom UI, it is possible to make it show up with the small “window” icon on the plug-in header.

For VST2 plug-ins with many controls, parameters can be exposed as needed for automation; see the parameter workflow below. Other formats use their own port models.

Common formats: CLAP, VST, VST3, LV2, JSFX

score hosts VST 2.4, VST3, CLAP, LV2 and JSFX through separate integrations. Availability depends on the build and platform; the plug-in binary must match the operating system and architecture of score. A format being supported does not guarantee that every plug-in, custom editor or optional extension works. AirWindows is also available as a collection of built-in effects.

Scanning and search paths

score provides separate VST, VST3, CLAP and LV2 tabs under Preferences → Effects. Each has its own search paths, Add path and Rescan buttons, plus Working plug-ins and Faulty plug-ins tables. Right-click a search path and choose Remove to remove it.

Install the plug-in for your OS and architecture.
Add its containing directory in the matching format tab, not another format’s tab. VST3 and VST2 no longer share a path list.
Use Rescan, then look for the plug-in in Working plug-ins and in the library.
If it is faulty, check its dependencies, architecture and installation before rescanning. A successful scan establishes discoverability, not complete runtime compatibility.

These formats are scanned in helper processes and their results are cached. VST_PATH, VST3_PATH, CLAP_PATH and LV2_PATH can supplement configured paths. Set SCORE_DISABLE_AUDIOPLUGINS=1 before launching score to suppress automatic audio plug-in scanning when diagnosing startup problems. Previously cached VST, VST3 and CLAP entries can remain available. SCORE_DISABLE_LV2=1 disables LV2 initialization/scanning specifically; it is not merely a way to hide its editor.

Save score process presets to reuse configured plug-ins. Do not assume that a vendor’s native preset-file format is interchangeable with score presets.

Controlling VST2 parameters

To be able to automate and connect VST parameters to other parts of the session, it is necessary to make them visible in the nodes. For plug-ins with less than a dozen parameters, they will always be shown by default. For plug-ins with more parameters, this is however opt-in.

The first button allows to show / hide the audio plug-in UI. The second, when enabled, means that the plug-in’s parameters will be checked for changes: whenever a value changes, it will appear in the score UI and be open to automation, etc.

Here is the complete procedure:

This parameter-exposure workflow applies to VST2. Other integrations expose controls according to their own port models.

VST3

Use the VST3 preferences tab for VST3 bundles; a VST2 installation of the same product is a separate plug-in. Route MIDI to instruments through their declared event input. Current hosting forwards CC, pitch bend and aftertouch through the plug-in’s VST3 MIDI mapping; the receiving plug-in must provide the corresponding mapping. Do not assume that controls or saved state are interchangeable between a product’s VST2 and VST3 versions.

CLAP

CLAP exposes the plug-in’s declared audio and note ports and automatable controls. The host handles CLAP note events, MIDI and MIDI 2 events, and forwards supported note/MIDI 2/SysEx output events to MIDI outlets. Non-note messages such as CC, pitch bend and pressure are also forwarded when the plug-in uses the CLAP note dialect. The dialects declared by the particular port still determine what it can receive; this is not a promise that every plug-in handles MIDI 2 or SysEx.

For replicated multichannel processing, a scalar control applies to each voice. A list or 2/3/4-component vector supplies per-voice values; if there are more voices than values, the last value is reused. This is host-side multichannel control, not a guarantee of per-note expression inside an instrument.

The host supports plug-in state-change notifications and restart requests. Try a plug-in in a small document, including save/reload and its custom editor, before depending on it in a performance.

LV2

LV2 requires a build with the LV2 hosting dependencies. Its search paths are independent of the other formats. Ports follow the bundle’s metadata: audio and CV ports are audio-rate connections, MIDI atom ports carry MIDI, and control ports become parameters. CV outputs are audio outlets, not scalar value outputs; cable CV inputs from an appropriate audio-rate source.

A mono effect with one audio input and one audio output can be replicated across a multichannel bus. This is one effect instance per channel, not automatic MIDI polyphony for every LV2 instrument. Scalar controls are shared; vector/list controls can supply per-voice values.

Custom UI support is narrower than DSP support. score selects an editor that its UI host can embed and whose binary exists. Editors linked against another Qt major version are deliberately rejected to avoid in-process conflicts. A working plug-in may therefore have no usable custom window; use its exposed controls.

Transport and reverse playback

VST2, VST3 and LV2 receive timeline transport positions and can continue processing when the timeline runs backwards. CLAP receives musical song position, and JSFX receives time, tempo and signature information. This does not make a delay, reverb or synthesizer run its internal history backwards. Transport-sensitive behavior remains plug-in dependent. Current LV2 hosting delivers stop/start changes and resets processing state for a new play.

Adding JSFX plug-ins

JSFX plug-ins can be added in the user library. Score will look for files ending with the .jsfx extension.

For programming syntax, code sections and audio/MIDI functions, see the JSFX and EEL2 language reference, which links to the official manuals and explains score’s hosting context.

If you are on Unix or a system with bash, you can rename the JSFX plugins without extensions this way:

$ find . -type f ! -name '*.*' -exec perl-rename 's/$/.jsfx/' {} \;

Here are some links to free JSFX collections:

Some JSFX plug-ins need separate data files. To ensure that they can find it, the following organization is recommended:

jsfx_folder/Effects/foo/effect.jsfx
jsfx_folder/Data/<matching data files>

For instance, a complete path on a Mac with the default user library location would look like:

/Users/you/Documents/ossia/score/packages/jsfx/Effects/dynamics/general_dynamics.jsfx
/Users/you/Documents/ossia/score/packages/jsfx/Data/amp_models/SomeImpulse.wav

score hosts JSFX through YSFX and provides a script editor for live code changes. Edited script text and controls are retained by process serialization and presets; copy/paste and undo/redo preserve the edited process rather than relying only on its original file path.

The custom graphics host supports resizing, menus, cursors and high-DPI drawing. Support still depends on the YSFX version compiled into score and on what the script uses. Presets whose names begin with bracketed tags can be grouped into submenus. Keep required data/import files alongside the library package even when the script text is saved in the document.

Advanced plug-in and extensions formats

It is also possible to use less common systems for audio processing:

Some of these plug-in systems, like Faust are source-based: that is, score will compile the source code of the plug-in directly, which can take a few seconds when dropping the plug-in in the session.

Preset support for these plug-ins is a work-in-progress.