thinksynth

thinksynth builds sounds out of a graph of DSP nodes — oscillators, filters, envelopes, delays and arithmetic — described in a small language and rendered in real time. Patches assign those graphs to MIDI channels, so one instrument can layer several voices.

Every node is a plugin, and the set that ships covers subtractive and FM synthesis, resonators, waveshaping and a range of filters. New ones are ordinary shared libraries dropped into the plugin directory.

cmake -S . -B build
cmake --build build
ctest --test-dir build
./build/src/thinksynth

On Debian or Ubuntu:

sudo apt install build-essential cmake ninja-build bison flex pkg-config \
    libgtkmm-4.0-dev libsigc++-3.0-dev libasound2-dev

Optional, and each one buys something specific:

sudo apt install libjack-jackd2-dev libpulse-dev \
    adwaita-icon-theme librsvg2-common xvfb

libasound2-dev and libjack-jackd2-dev are there for RtAudio, not for thinksynth: no source in this tree includes an ALSA or a JACK header. RtAudio and RtMidi are the single audio and MIDI API the whole program talks to, and they are normally built from source as part of the build — a system copy is used only when pkg-config reports 6.0.0 or newer, which Ubuntu does not ship (24.04 has no librtaudio-dev at all and 22.04 has 5.2, which is a different API). So building RtAudio's Linux backends is part of building thinksynth, and those headers are what it needs.

Which is also why the JACK and PulseAudio ones are optional: CMake probes for them and compiles those backends in only if they are there. ALSA is always on. The configure summary says what you ended up with, including whether RtAudio came from the system or from source.

The rest are runtime or test-time. adwaita-icon-theme and librsvg2-common give the icons their intended look, and xvfb is needed by ctest because one gate builds real widgets.

Useful options:

Running an uninstalled build works: thinksynth tries ./plugins first and then the directories around its own binary, and THINK_PLUGIN_PATH overrides both.

Audio goes through RtAudio and MIDI through RtMidi, so the same build talks to ALSA, JACK, CoreAudio, WASAPI, CoreMIDI and WinMM without a per-backend code path.

thinksynth -d rtaudio          # the default
thinksynth -d jack             # JACK directly
thinksynth -d none             # no audio device; useful headless

The audio API and device are remembered in thinkrc, and the preferences dialogue lists what the machine actually has — RtAudio enumerates devices, so there is nothing to type.

thinkrc lives under the platform's config directory — ~/.config/thinksynth/thinkrc on Linux, ~/Library/Application Support/thinksynth/thinkrc on macOS, %LOCALAPPDATA%\thinksynth\thinkrc on Windows. A ~/.thinkrc from an older version is still read if no current one exists, but is never written back to.

There is nothing to set up. With no configuration file anywhere, thinksynth writes one and starts with four channels already loaded:

channel 0,leads/SuperRes.patch,30
channel 1,bass/FunkMachine.patch,30
channel 2,organs/Organ1.patch,30
channel 3,pads/SynString.patch,30

So the on-screen keyboard makes a sound immediately, and the channel spinner moves between four different ones. Edit or delete lines to change that; delete the whole file to get the defaults back.

The patches are named relatively and looked up the same way DSPs are, which is what lets the file survive the install moving — a .app, a Windows zip and a Flatpak all live somewhere the build never knew about. THINK_PATCH_PATH overrides where they are searched for.

On Windows, launching thinksynth does not open a terminal alongside it — it is a GUI-subsystem program. Run it from a terminal and it prints there anyway, so -h, -G and every diagnostic still work when you want them; redirection (thinksynth.exe -h > log.txt) works whether or not a terminal is involved.

For MIDI, connect an external sequencer or keyboard to thinksynth's input port using whatever your platform uses for that (aconnect or a patchbay on Linux, Audio MIDI Setup on macOS). Assign a DSP to each channel the MIDI uses and turn up the amplitudes. The on-screen keyboard works without any of this.

If you want JACK on Linux, start jackd before thinksynth — RtAudio will use the running server.