ReaSampler

Version 1.4.0 · License: GNU AGPL v3 (see LICENSE)

A per-project audio sample-bank capture tool for REAPER, built as two artifacts: a native C++ REAPER extension (reaper_reasampler) and a Windows-only VST3 sampler instrument (reasampler_9000.vst3, ReaSampler 9000). It captures any arbitrary audio source into a per-project sample bank (cached files + a docked grid), decoupled from the arrange view, with keyboard/MIDI-bindable capture and placement. It is designed as a precision tool: deterministic captures, non-destructive by construction, no auto-inserted clutter.

Status

Under active development, not yet formally released.

The two artifacts

reaper_reasampler — the REAPER extension. Captures audio into a named, per-project sample bank and provides bindable actions across the workflow: offline and realtime capture (with cancel), batch capture (per selected item or per razor area), recapture-from-source, capture-and-assign to a live instrument instance, insert with an opt-in tempo-conform variant, the resample-bake landing action, multi-bank management (pool, activate, evacuate, move, copy, delete), prune/reclaim, provenance and lineage tracking, Design View, and ingest via drag-out, arrange-drop, and instrument-drop. All of it surfaces in a docked bank panel.

ReaSampler 9000 (reasampler_9000.vst3) — a Windows-only VST3 sampler instrument that plays bank captures back across a MIDI keyboard. Since ComponentState v10 it is self-contained: it decodes samples from its own persisted references and plays with the extension absent, treating the bank as a browsing source rather than a runtime dependency. The VST3 target (reasampler_vst) is gated on WIN32 AND EXISTS .../pluginfactory.cpp — omitted on macOS/Linux even when the vendored vendor/vst3sdk slice is present, and quietly omitted anywhere the slice itself is absent.

A beta channel build is available via -DREASAMPLER_CHANNEL=beta at configure time, producing reaper_reasampler_beta and reasampler_9000_beta.vst3. The two channels coexist in one REAPER installation and do not share state.

The load-bearing principle

Capture and placement are separate acts. Capturing audio writes a file to the bank and adds an index entry. It never puts an item in the arrange view. Placement is a distinct, on-demand action. Any code path that auto-inserts a capture into the timeline violates the purpose of the tool.

Prerequisites

• CMake ≥ 3.19
• A C++17 compiler
• Windows + MSVC to build the VST3 target (reasampler_vst) — the REAPER extension itself is cross-platform
• PHP, to run the SWELL resource-generation step on macOS/Linux (below)

Platform support

The REAPER extension targets Windows, macOS, and Linux; ReaSampler 9000 (the VST3 instrument) is Windows-only.

Platform	Extension	VST3 instrument
Windows	Builds with no extra steps	Builds when vendor/vst3sdk is present
macOS	Builds, but dialogs need the manual SWELL resgen step below plus hand-uncommenting the APPLE target_sources block in src/app/CMakeLists.txt	Not built (Windows-only gate)
Linux	Same manual resgen + hand-uncomment requirement as macOS, against its own commented block	Not built (Windows-only gate)

A macOS/Linux build that skips the resgen-and-uncomment step compiles cleanly without dialogs and without a warning — this is expected, not a bug.

One-time setup

A plain git clone --recursive also works, but it pulls every nested submodule of vendor/vst3sdk (including vstgui4, tutorials, doc, cmake — none of which this project links against). The steps below pull only the three submodules actually needed:

git submodule update --init

Vendors three submodules:

• vendor/reaper-sdk — sdk/reaper_plugin.h, sdk/reaper_plugin_functions.h, SWELL headers

• vendor/WDL — WDL utilities and the SWELL cross-platform Win32 layer

• vendor/vst3sdk — Steinberg VST3 SDK (Windows-only; requires a nested init after the top-level init):

  git submodule update --init vendor/vst3sdk
  cd vendor/vst3sdk && git submodule update --init pluginterfaces base public.sdk
  

Build and test

cmake -B build -S .
cmake --build build
ctest --test-dir build -C Debug

On a multi-config generator (Visual Studio, Xcode), cmake --build build with no --config builds Debug — nothing in this build sets CMAKE_BUILD_TYPE or an optimization flag, so that's the default. The -C Debug above is required on a multi-config generator too: without it, ctest silently reports every test as "Not Run" instead of running them. Single-config generators (Ninja, Make) need neither flag.

Pure core/ modules each have a corresponding <module>_tests executable target that runs without REAPER or a DAW. Targets are declared per-directory — each src/**/CMakeLists.txt owns its own libraries and test targets, pulled in via add_subdirectory from the root CMakeLists.txt, which itself declares no targets directly.

Installing or judging performance requires the Release config explicitly:

cmake --build build --config Release
ctest --test-dir build -C Release

Beta channel

cmake -B build-beta -S . -DREASAMPLER_CHANNEL=beta
cmake --build build-beta

macOS / Linux dialog resources

src/resource.rc must be pre-processed by SWELL's resgen once per platform:

php vendor/WDL/WDL/swell/swell_resgen.php src/resource.rc   # macOS; Linux reuses the output

Add the generated file to the appropriate APPLE / Linux target_sources block in src/app/CMakeLists.txt (both are commented out by default). The SWS extension build is the canonical reference for this step.

Install

There is no hot reload; REAPER loads extensions at startup only.

Extension — copy the Release build's reaper_reasampler binary (build/Release/ on a multi-config generator — not the default Debug/ output) into REAPER's UserPlugins/ folder (Options → Show REAPER resource path), then restart REAPER.

VST3 instrument — copy the Release build's reasampler_9000.vst3 into the system VST3 folder (C:\Program Files\Common Files\VST3 on Windows) — a different destination from the extension, not UserPlugins/. REAPER picks it up on its next plugin rescan.

Repo layout

The codebase is organized around one discipline: pure, REAPER/VST3-SDK-free testable core, split from the REAPER- and VST3-facing shells that touch those host types.

• src/app/ — the REAPER extension's entry point (main.cpp only)
• src/core/ — pure modules, no REAPER or VST3 SDK types, each with a <module>_tests target: audio/, capture/, instrument/ (further split into bake/, engine/filter/, engine/loop/, map/, note/, ui/), json/, model/, reclaim/, tracking/, ui/, util/, version/, view/, wire/
• src/shell/ — REAPER/VST3-facing shells: actions/, bank_ops/, capture/, instrument/ (the ReaSampler 9000 VST3 shells), panel/, persist/, view/
• src/resource.rc, src/resource.h, src/ext_keys.h — root-level build inputs not claimed by any one subdirectory
• tests/ — unit test sources for the pure core/ modules
• cmake/ — shared CMake target-declaration helpers
• docs/ — plan-style docs and product-design docs (see Further reading, below)
• vendor/ — git submodules

See CLAUDE.md for the full module inventory, architectural contracts, and the precise boundary between pure core and REAPER/VST3-facing shells; each src/**/ directory also carries its own CLAUDE.md with that area's own module list and invariants.

License

GNU AGPL v3, copyright Daniel Harvey. See LICENSE.

Further reading

• CLAUDE.md — architecture, module inventory, and build/API contracts
• docs/PLAN.md — the active roadmap
• docs/COMPLETED.md — landed milestones for the current (1.x) cycle
• docs/TODO.md — deferred follow-ups, with the reason each was deferred
• docs/TODO-1.0.md — the raw 1.x work list this cycle's plan was structured from
• docs/ARCHIVE.md — pre-1.0 history
• docs/cmake-cheatsheet.md — a standalone build-system reference
• docs/product/ — the product-design reasoning behind each phase