Bastl Instruments - Kastle 2 Alchemist

Kastle 2 Alchemist is Bastl’s latest tiny sound box that acts far bigger than it looks: a patchable hybrid synth voice, pattern generator and USB-MIDI brain that fits in your hand. It’s monophonic on paper, but between its pitch logic, built-in harmony tricks and effects it happily drifts into “how is that only one voice?” territory.

You get five synth modes (FILTER, FM, SUPERSAW, HYPERSINE and GLITCHNOISE) under a single TIMBRE control, with RATIO refining detune and wave mixing ratios per mode. With this, you can sweep from clean subtractive tones to noisy textures and fizzy supersaws without any sort of sub-sub-menu headache. The ENV control ties envelope, timbral focus, and even mode morphing together, so one knob push-pulls the sound between sharp plucks, sustained bodies, and full-on drones, an ultra-macro of sorts.

Instead of a traditional step sequencer, pitch is driven by a smart little system of inputs. The PITCH knob sets your base, NOTE input gives you quantized scales, and PLAY adds automatic 3rd/5th/octave harmonies locked to an internal grid. With this, you can set up evolving arpeggios, shifting harmonies, and generative lines just by patching gates and CV around, or customize scales and rhythms via the web editor when you want even more control.

Over at the effects side, you'll find a dual FX engine that can add stereo delay on one side and a chorus/flanger/distortion/comb-filter macro on the other, tuned differently for each synth mode. With this, you can smear simple patterns into lush echoes, dirty resonances, or wide stereo washes, and you can even run external audio through the FX via the stereo input. Add clockable LFO, analog sync I/O, and full USB-MIDI in and out, and Kastle 2 Alchemist becomes a pocket companion that can just as easily drive your DAW as jam with other battery-powered boxes.

Throw it in a bag with a handful of patch cables, power it from three AA batteries or USB-C, plug in headphones, and you’re off! Instead of writing melodies step by step, you set up behaviours — scales, rhythms, routings — and let the Alchemist (true to its name) feed you ideas. You can treat it like a small synth, a weird controller, or a generative sketchpad; it’s happiest when you let it surprise you!

Features:

Synthesis & Sound

• 5 synthesis modes: Filter, FM, Hypersine, Supersaw, Glitchnoise
• 4-oscillator hybrid architecture with FM feedback, ring mod, and waveform mixing
• Stereo filtering and noise generation
• Dual FX: delay (left) + chorus/flanger/distortion (right)
• Pitch slide with envelope and portamento
• Stereo audio processing at 44kHz/16-bit

Sequencing & Modulation

• Pattern generator with CV and GATE outputs
• Syncable LFO with triangle and pulse waveforms
• User-programmable rhythm patterns via web app
• Quantized pitch with customizable scales
• Tap tempo with clock divider

Controls & I/O

• Patchable inputs for pitch, timbre, envelope, and mode modulation
• Stereo audio input with gain control (up to +12dB)
• Stereo headphone output (up to 250 Ohm)
• Analog sync in/out with modular CV capability
• USB MIDI input and output (notes, clock, CCs)

Portability

• Pocket-sized format
• Runs on 3 AA batteries (15-18 hours) or USB-C
• Includes 10 patch cables