VST3Go

vst3go is the low-level Go interface and runtime layer for VST3.

This fork is intentionally different from the original justyntemme/vst3go project. It is being kept deliberately narrow as a clean VST3 binding/runtime layer, while the higher-level DSP and synth-oriented functionality lives in the companion synthkit repository.

It contains:

• VST3 C API headers and C bridge glue
• Go bindings for VST3 types and process structures
• The plugin wrapper/runtime used to expose Go processors as VST3 plugins
• Generic plugin authoring primitives such as buses, parameters, process context, state, and MIDI/event transport

The higher-level audio and synth layer now lives in the companion synthkit repository.

Scope

vst3go keeps the VST3-facing pieces:

• bridge/
• include/vst3/
• pkg/vst3/
• pkg/plugin/
• pkg/midi/
• pkg/bundle
• pkg/framework/bus
• pkg/framework/param
• pkg/framework/plugin
• pkg/framework/process
• pkg/framework/state

The companion synthkit repo owns:

• pkg/dsp/
• pkg/framework/dsp
• pkg/framework/debug
• pkg/framework/voice
• examples/

Companion Repo

Recommended name: synthkit

Purpose:

• DSP building blocks
• instrument/effect showcase plugins
• higher-level audio helpers built on top of vst3go

Platform support

Platform	Builds	Smoke test	Validator
linux/amd64	CI	CI	CI
darwin (amd64, arm64)	CI	—	—
windows/amd64	CI	CI	—
windows/arm64	—	—	—

A plug-in is not a bare shared library on any of these: it is a .vst3 bundle directory with a per-architecture subdirectory inside. pkg/bundle computes that layout, so build scripts do not have to hard-code it:

l, err := bundle.For("MyPlugin", runtime.GOOS, runtime.GOARCH)
binary, err := l.Create(outputDir)  // where to write the c-shared build

Windows needs MinGW-w64 (MSVC cannot be driven by cgo) and has enough platform-specific behaviour — DLL file locking, the Go runtime's unload constraints, MAX_PATH — to warrant its own page: docs/windows.md.

Consuming this repo

The module path is github.com/cwbudde/vst3go, and go get is enough:

go get github.com/cwbudde/vst3go

The VST 3 C API header is vendored in include/vst3, so a copy downloaded from the module proxy compiles. It did not until recently, and a replace directive pointing at a checkout was the documented workaround; if you are carrying one, docs/migration.md has the removal. That file also covers the versioning scheme, the accumulated breaking changes (preset format v2, the midi.Event rework, the bypass-flag rule), and the deprecated parameter accessors.

Vendoring the header means this repository redistributes it, which only Steinberg's GPLv3 alternative permits. See License below --- it changes nothing about the terms for a plug-in you build, which were always the same, but it is worth reading once.

Development

Core checks in this repo:

just fmt
just fmt-check
just test

Two heavier checks sit behind build tags. The first builds the runtime into a real loadable module, drives it from C, and checks the module actually exports the entry points a host resolves by name; the second runs Steinberg's own conformance suite against it.

just test-smoke                                   # go test -tags smoke ./test/smoke/...
VST3_VALIDATOR=/path/to/validator just test-validator

With a MinGW-w64 toolchain installed, just test-smoke also cross-builds the Windows DLL and inspects its export and import tables. just build-windows does the cross-build on its own.

docs/validation.md explains what each of these covers, and — more importantly — what a downstream repo such as synthkit still has to validate on its own.

License

This project's own source is licensed under the MIT License — see LICENSE.

The VST 3 C API headers are redistributed here, in include/vst3, under Steinberg's dual license (the VST 3 License Agreement or GPLv3). Only the GPLv3 alternative permits that redistribution — the proprietary license forbids distributing the SDK in parts without a signed agreement — so the copy you get from this repository comes to you under the GPLv3, whose full text is in COPYING. Three license files, for three different things: COPYING is the GPLv3 the headers come under, LICENSE is this project's own MIT license, and include/vst3/LICENSE.txt is Steinberg's dual-license notice, carried verbatim with the headers.

That does not change the terms for a plug-in you build. A compiled plug-in is a combined work with those headers either way, so the terms under which you may distribute a binary come from whichever Steinberg license you have accepted — without a signed agreement, that is the GPLv3. See the third-party notice in LICENSE for details.