Hosting Synths & Samplers
The same plugin host that runs your guitar effects also runs over 60 synths, samplers, and drum machines — and a USB MIDI keyboard plugged into any of the pi-Stomp's USB-A ports works out of the box. You can build a pedalboard that's an instrument, not just an effects chain, and play it from the floor with no computer on stage.
Plugging in a keyboard
- Connect a USB-MIDI keyboard to any USB-A port on the pi-Stomp
- Open MOD-UI at http://pistomp.local
- Your keyboard appears under Hardware Capture in the plugin browser's MIDI section, usually as an ALSA client name like
USB MIDI Keyboard
USB-MIDI class-compliant keyboards work without any driver install. DIN MIDI needs the MIDI + Expression Add-On Kit.
Adding a synth
Drag a generator plugin onto the canvas — same as an effect. The plugin browser groups them under Generator. A few worth knowing:
| Plugin | What it is |
|---|---|
| setBfree | Hammond B3 tonewheel organ emulator with drawbar control |
| AMSynth | Analog-modelling synth, single voice |
| Calf Mono Synth | Subtractive synth with built-in envelope and filter |
| Hexter | Yamaha DX7-style FM synth |
| Qsynth / FluidSynth | General MIDI soundfont player — point it at a .sf2 file |
| SooperLooper | Looping sampler |
| drum machines | Several beat and drum plugins under Generator |
The full list is on the All Plugins page — filter by Generator.
Wiring MIDI to audio
A generator plugin takes MIDI in and produces audio out:
- Drag a cable from your keyboard's MIDI output to the synth's MIDI input
- Drag a cable from the synth's audio output to the pedalboard's hardware playback (or to another effect, then to playback)
MIDI cables in MOD-UI are the same orange as audio cables — the ports are typed, so you can only connect MIDI to MIDI and audio to audio.
Mapping hardware to it
Footswitches and expression pedals work the same way on a synth as on an effect. Common bindings:
- Expression pedal → organ drawbar (or any continuous parameter)
- Footswitch → preset change for patch switching
- Tweak encoder → filter cutoff for wah-style sweeps
See MOD-UI for the assignment flow.
MIDI to CV
If you'd rather drive a modular synth, the MIDI to CV plugin converts note pitch to control voltage (1/12 V per semitone, plus a gate) — internal only, since the pi-Stomp has no CV jacks on the enclosure. The full CV toolkit is on that page.
CPU cost
Generators are the heaviest CPU category on the device. A single polyphonic synth can eat more headroom than a full guitar chain. Watch the CPU meter in MOD-UI's top bar; if you're hitting XRUNs, see Performance Tuning.