Bastl Instruments Citadel Alchemist

The Bastl Instruments Citadel Alchemist is a hybrid synth voice designed to thrive on modulation, experimentation, and happy accidents. Originally known as the Kastle 2 Alchemist, this curious little instrument now lives comfortably in 16HP Eurorack format, gaining all the flexibility and patchability that modular systems invite.

Like the other Citadel series modules, the Alchemist shares a common hardware platform with Wave Bard and FX Wizard. The firmware is fully cross compatible, meaning you can freely swap personalities whenever you feel like it. Load Wave Bard for a stereo sampler, FX Wizard for multi effects, or return to Alchemist for generative synthesis. Bastl even provides a reversible faceplate, with Alchemist graphics on one side and a blank panel on the other for your own labelling. It is effectively three instruments in one, and Bastl are partially open sourcing the platform for deeper exploration.

At its core, the Alchemist is a hybrid synth voice built around five synthesis modes: Filter, FM, Supersaw, Hypersine, and Glitchnoise. These modes are continuously swept using the main Timbre control, allowing smooth transitions between radically different sound engines. Pitch inputs are quantized, with scales defined via a simple web based editor, encouraging melodies to emerge organically from modulation rather than traditional sequencing. The result is generative, unpredictable, and often surprisingly musical.

Under the hood, the engine combines four oscillators with FM feedback, ring modulation, a stereo filter, and a transient shaper. The ENV macro goes far beyond amplitude shaping, morphing between synthesis modes, adjusting envelope times, and even slowing arpeggios at higher settings. A dual effects section rounds things off, with stereo delay on one side and a chorus, flanger, and distortion chain on the other, each carefully tuned to suit the active synthesis mode.

Despite its experimental nature, the Citadel Alchemist is highly self contained. It includes a headphone output, TRS MIDI input, tap tempo clock with divider, pattern generator, and internal LFO. It also sends USB MIDI out, allowing your modular generated ideas to control software or external hardware.

For small systems, beginners, or anyone looking for a compact melodic voice that rewards curiosity and hands on patching