Bastl Instruments Kastle 2 Alchemist, the successor of the Kastle ARP, is a patchable hybrid Synthesizer designed for evolving melodies.
In mid-November 2024, Bastle Instruments introduced the Kastle 2, the next generation of their small, semi-modular synthesizers—same concept, but with more power, USB-C, and more.
The last Kastle of the first generation was the Arp, released in 2023, an exciting melodic Synthesizer which I also covered in a video. This was discontinued a year later when Kastle 2 was released. Bastl Instruments is now reviving the concept in the form of Kastle 2 Alchemist.
Bastl Instruments Kastle 2 Alchemist
Kastle 2 Alchemist is a patchable Synthesizer that empowers you to discover melodies and even harmonies despite its monophonic nature.
Not only is Kastle 2 Alchemist the successor to Kastle Arp, but Bastl Instruments has also taken the concept further and raised it to the K2 level. This is especially true in the sound spectrum.
Kastle 2 Alchemist now features five distinct synthesis modes, including FILTER, FM, HYPERSINE, SUPERSAW, and GLITCHNOISE, selectable via the main timbre knob and refined by the ratio control.
The timbral menu is further expanded by a new dual FX section, offering various FX algorithms to choose from.
You can either explore a wide delay that will smear the arpeggios into echo harmonies or a multi-FX chain (chorus, flanger, distortion, comb filter) custom-tuned for each synth mode.
In direct comparison, this is a big step forward. I really like the Kastle Arp, but its sound spectrum is too limited. This one is significantly more versatile.
Evolving Sequences
Like the Kastle Arp, the Kastle 2 Alchemist is an endless source of melodies. The way to achieve them is the same. Patch the sequencer signals (CV/gate) into the two pitch mod inputs, and the engine makes you happy with an endless world of arpeggio melodies.
Thanks to the quantized oscillator, you are always on the safe side with the tuning. Bastl Instruments also added the option to customize the Kastle 2 Alchemist’s rhythms and scales via the web-based app.
The central ENV control, which acts as a macro control for the entire engine, is also part of it. Even if it sounds like an envelope macro control, it does more than that.
It affects different parts of the synth and even the sequencer engine to maximize musicality. According to Bastl, you can also use it to morph between synthesis modes continuously. That sounds like a lot of fun.
A syncable LFO brings additional movement to your sounds. It can also be modulated via the dedicated LFO mod, making it both versatile and unpredictable.
Further, it includes a new pitch slide macro that applies pitch envelope and portamento to your sounds, enabling gliding rubber textures.
Customizable & Portable
The Kastle 2 Alchemist is just as “hackable” as its siblings. With the built-in USB-C port, you can easily swap the firmware and explore other Kastle 2 engines, including the Wave Bard sample player and FX Wizard multi-fx unit.
It is also super portable. The Alchemist runs on three AA batteries or via USB-C so that you can explore anywhere, anytime. Alongside this, you have sync in and out for jamming with other portable gear.
There is also an audio input for mixing external signals or running them through its built-in effects, or, if you use the alternative firmware, FX Wizard. On the right side, you also have an audio output.
Bastl Instruments Kastle 2 Alchemist: First Impression
As a user of the first Arp, I’m happy to see that the concept lives on in Kastle 2 Alchemist. The sound engine is now significantly more powerful, making it more enjoyable for longer. Check out the sound demos on their website.
And something often overlooked: Buy one Kastle 2 and you can discover all three firmware by simply swapping the firmware.
Bastl Instruments Kastle 2 Alchemist is available now for 192€, including tax.
More information here: Bastl Instruments
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