Bastl Instruments released firmware 1.7 for the Kastle 2 and the Citadel eurorack series on 2 September 2026. The update is free for existing owners and runs on all three Kastle 2 variants: the Alchemist, the Wave Bard and the FX Wizard.
What the update adds
The sequencer engine gains humanize and swing. Bastl says humanize shifts a pattern's triggers with a knob twist, producing a different output from the same sequence. From 1.7 onwards those shifts apply to the CV and gate outputs, and both parameters respond to MIDI CC32.
LFO modulation also becomes assignable, so an LFO can be routed to a chosen parameter from the advanced settings. The Alchemy firmware picks up MIDI velocity and sustain. Bastl lists bug fixes alongside the new features.
The hardware
The Kastle 2 is a patchable, battery-powered pocket synth. Bastl lists power from three AA batteries or USB-C, 15 to 18 hours of battery life, a stereo output rated for headphones up to 250 ohms, an analog sync output, CV and gate outputs, and USB MIDI in and out.
Alternative firmware
Bastl open-sourced the Kastle 2 platform earlier in 2026 and published the schematics and code on GitHub. Several people have since written their own engines for the hardware.
- Knoscillator, by ddf, a stereo oscillator built on parametric 3D curves, with a sequencer and a delay.
- Glazmo Kastle2 Skrub, by Oliver Torr, which records segments of an audio buffer and plays them back in harmonic or chaotic modes.
- Glazmo Kick, also by Oliver Torr and still to come, a synthesized 808-style kick engine with style options.
- Kastle Chan v1.0, by sxilence6, a patchable vocal engine.
Via Synth Anatomy. More at Bastl Instruments.