Fontelle

A lightweight, Linux-first digital audio workstation built around SoundFont-based sample playback. An SF2 file supplies defaults — loop points, envelopes, filtering, mapping, tuning — and every one of them is yours to override. Free and open source, by Fopull LLC.

Status: early access, and a working studio. There is a window you can write a whole piece in; there is still a great deal on the design's list. See Project status.

Installing

Download from https://fopull.com/fontelle

• Linux (the platform this is built for): unpack the tarball and run ./install.sh. It puts fontelle in ~/.local/bin with a menu entry and an icon — nothing outside your home folder, no root. ./install.sh --uninstall takes it away again. The binary needs ALSA and D-Bus from your distribution, which nearly every desktop has; the installer says so if anything is missing.
• Windows / macOS: unpack and run fontelle. The binaries are unsigned for now, so expect the first-run warning (macOS: right-click → Open).

Fontelle checks for a newer release when it starts and offers to install it from its start menu — the download is verified against the release's published checksums before anything is replaced. The check can be turned off on the Settings tab.

Why

Every existing SoundFont player treats the file's internal parameters as authoritative. Fontelle inverts that: the SF2 supplies a starting point, and nothing about it is locked. See FONTELLE_TDD.md for the full design — product thesis, invariants, crate layout, milestones, and the open questions still to resolve.

Running it

fontelle                          # installed
cargo run --release -p fontelle-app   # from a checkout

That opens the start menu: your recent projects, New project, Open a project…, and whether there is a newer Fontelle. Pick one and you are in the studio — a channel rack, a soundfont browser, an arrangement, a piano roll and a mixer, over a real audio device. --no-menu skips the menu; --help lists the rest.

Your soundfonts live in a folder Fontelle scans, shown at the bottom of the browser. Open folder shows you that folder in your file manager, creating it if it is not there yet — drop your .sf2 files in and they appear. Change… picks a different folder (Ctrl+click to add one alongside rather than replace), and the choice is remembered. The default is ~/.local/share/fontelle/soundfonts; there is a command-line equivalent if you prefer:

cargo run --release -p fontelle-app -- --soundfonts /path/to/your/soundfonts

Then: pick a soundfont in the browser, pick a preset (a plain click puts it on the selected channel; Ctrl+click puts it on a new one), and draw.

Draw / delete a note	left mouse / right mouse
Draw one to length	drag out from an empty cell
Lengthen one	drag its right edge
Tools	P draw, B paint, E select, D delete
Snap	S cycles bar / beat / 1⁄8 / 1⁄16 / 1⁄32 / triplet / off
Off the grid, one axis	hold Alt, hold Shift
Select a region	the Select tool, or Ctrl+drag
Clipboard	Ctrl+C / X / V, Ctrl+B duplicate
Undo / redo / save	Ctrl+Z / Ctrl+Y / Ctrl+S
Play	Space
Scroll	wheel for pitch, Shift+wheel for time
Zoom, about the pointer	Ctrl+wheel for time, Ctrl+Shift+wheel for pitch
Find a soundfont	Ctrl+F, then type — it matches letters in order, so gus finds GeneralUser GS
Every shortcut	F1, or the ? on the start menu and the transport bar — click one there to change it

The command line is still there and does more than the window does — offline WAV bounces, MIDI file import, live MIDI in, recording a take. --play-sf2 <file> plays a demo phrase through a preset; add --window to open the same project in the editor, --open <project.fontelle> to reopen a saved one.

Project status

Early access. Everything below is built, tested and used; the design in FONTELLE_TDD.md goes further, and PROGRESS.md is the blunt, living account of where each part stands — read it before trusting this list.

Composing. An arrangement with lanes and clips (MIDI, audio, automation), looping, stretch and cut, fades, a blade, and prefabs; a piano roll with draw, paint, select and delete tools, snap down to 1/32 and triplets, a property lane, ghosts, an arpeggiator and legato joining; slides and pitch bends; full undo, autosave and backups; project bundles that reopen with their audio.

Sound. The SoundFont sampler with every parameter user-owned and automatable; Flopsynth, the built-in synthesiser, with a 338-preset bank; a physically-modelled drum machine; sampler channels from imported audio; live MIDI with hot-plug, MIDI recording, MIDI and FL Studio score import; audio import, recording with monitoring, an audio clip editor, and offline rendering to WAV.

Mixing. A mixer with sends, routing and a master bus with a brickwall limiter; insert chains with wet/dry and delay compensation; track presets; twelve built-in effects, each a family rather than one sound — Utility, EQ, Filter, Compressor (with sidechain), Gate, Distortion, Bitcrush, Soften, Chorus, Delay, Reverb and Tune, an autotune.

Plugins. CLAP, VST 3 and LV2 instruments and effects, with their own editor windows and their state in the project, on Linux, Windows and macOS.

Vital's window on NVIDIA (Linux). Vital draws with EGL into the X server's root window, and NVIDIA's EGL offers what Vital asks for (an alpha channel) only with a 32-bit visual, which the root window does not have — so Vital aborts (BGFX FATAL ... Failed to create surface) in any host, and in Vital's own standalone app. Fontelle checks for this before it opens Vital's window (in a separate process, once a session): where the driver cannot draw it, the window is not opened, the status line says why, and Vital's knobs are in Fontelle's own panel.

To use Vital's window there, turn on Settings → Compatible plugin graphics and restart Fontelle. Plugin windows that draw with OpenGL through EGL then use Mesa's EGL — on the CPU (llvmpipe) unless Mesa has a GPU driver for your card: slower, but they open. Fontelle's own window draws with Vulkan and is not affected, nor are plugins that use OpenGL through GLX (JUCE's and DPF's, such as the Dragonfly reverbs). The row is greyed out with the reason when Mesa's EGL is not installed. The same, by hand, for one run:

__EGL_VENDOR_LIBRARY_FILENAMES=/usr/share/glvnd/egl_vendor.d/50_mesa.json fontelle

Adding MESA_LOADER_DRIVER_OVERRIDE=zink puts Mesa on the GPU instead, through Vulkan.

Not built. VST2/VST3 hosting (a bridge is designed, out of tree), plugin export, sample streaming (a soundfont is fully resident), and the later milestones of the design. Windows and macOS builds come off the same release workflow as Linux and are less exercised.

See docs/scaffolding-notes.md for the one structural decision made during scaffolding that isn't explicit in the TDD.

Building

Requires Rust 2024 edition (MSRV 1.88.0). On Linux you'll also need ALSA, the JACK headers (JACK itself is loaded at run time, only if it is there), D-Bus (for rtkit) and windowing/XKB development headers. LV2's lilv is built from vendor/lilv on every system, so it needs only a C compiler:

sudo apt install libasound2-dev libjack-jackd2-dev libudev-dev libxkbcommon-dev libwayland-dev \
    libxcb1-dev libxcb-render0-dev libxcb-shape0-dev libxcb-xfixes0-dev \
    libdbus-1-dev

cargo check --workspace

Releasing

One version number for the whole workspace, in the root Cargo.toml. Bump it, commit, then tag and push:

git tag v0.2.0 && git push origin v0.2.0

release.yml refuses a tag that does not match the version in the tree, builds the Linux, Windows and macOS archives, and publishes them with a SHA256SUMS — which is what the start menu's updater reads.

License

Dual-licensed under MIT or Apache-2.0, at your option — everything except one separate program:

fontelle-asio (crates/fontelle-asio-host/) is licensed GPL-3.0-only (its own LICENSE). It hosts an ASIO® driver for Fontelle on Windows and is built with Steinberg's ASIO SDK under the SDK's GPLv3 option (Steinberg's terms are in STEINBERG-ASIO-SDK-LICENSE.txt). It is a program of its own, shipped beside fontelle.exe in the Windows download; Fontelle starts it and exchanges plain audio data with it through shared memory, never linking it or loading its code, and it never loads Fontelle's code or any plugin. The protocol between them, which is MIT/Apache like the rest (crates/fontelle-audio-ipc/), is documented in docs/asio.md. ASIO is a registered trademark of Steinberg Media Technologies GmbH.

The ASIO Compatible Logo (assets/trademarks/asio/) is Steinberg's trademark, copied unaltered from their SDK and used as their guidelines require. It is not covered by any of the licences above; see its NOTICE and licenses/TRADEMARKS.md.

The factory Grand Piano's recordings (assets/flopsynth/samples/grand-stereo/, and the earlier mono cut in assets/flopsynth/samples/grand/) are cut from the Salamander Grand Piano by Alexander Holm, published under CC BY 3.0 and assembled as a soundfont by the FreePats project; they stay under that licence, with that credit.

The factory kits' recordings (assets/flopsynth/samples/kit/) are Fontelle's own drum machine, cut hit by hit; assets/flopsynth/samples/kit/README.md says how. Every sound Fontelle ships is listed, with its licence's text, in licenses/SOUNDS.md; a sound under a licence that does not allow redistribution (non-commercial, no-derivatives, personal-use-only) is refused by the build.

The note detection model (crates/fontelle-analysis/models/) is Spotify's basic-pitch, Apache-2.0, Copyright 2022 Spotify AB; its licence and notice are in licenses/basic-pitch/, and licenses/MODELS.md records the exact file.

"SoundFont" is a Creative/E-mu trademark and is used here only descriptively.