Who said 2020 was devoid of holiday spirit? Nerd Santa Claus* came through, at least, because Bastl Instruments have made a quirky, sexy good time in the Kastle Drum, a drum-focused follow-up to their adorable Kastle.

Kastle was already a cute, eminently usable little bit of kit. The open source project runs on batteries and lets you patch together clever little synth parts.

Kastle Drum takes that same micro-modular hardware and reimagines it in a new version made for “algorithmic industrial glitchy drums.” You can run its clock on its own and make stepped patterns, or jack in some analog clock from whatever you like (hardware, iOS apps, computer).

It’s an exercise in minimalism, but that’s the beauty of it. Instead of a big, expensive box parked on your desk with loads of presets up to your neck, you have to get clever with the pitch control, the onboard patch points, and envelopes. It’s definitely tiny, but provided you’re okay with some fine-fingered work, there are plenty of possibilities here.


8 drum synthesis styles

”noises” output for less tonal content

DRUM selects drum sounds

acceleration charge dynamic envelope

decay time

PITCH control with offset and CV input with attenuator

voltage-controllable clock with square and triangle output

stepped voltage generator with random, 8 step and 16 step loop mode

2 I/O CV ports that can be routed to any patch point

the main output can drive headphones

3x AA battery operation or USB power selectable by a switch

open source

durable black & gold PCB enclosure

10 patch cables and a sticker included

There’s a full manual, and you can run on either 3x AA batteries or Micro USB for power. (Batteries not included, but I bet you’ve got a Micro USB cable around.) Like its predecessor, the Kastle Drum is fully documented on GitHub.

You could use it on its own – there’s an onboard headphone jack and since it is battery powered, the palm of your hand is a workable studio space. But you can also interface it with other gear – two ins, two outs.

I’m not sure what a non-durable PCB would be like. Just don’t step on it, okay? But I can absolutely testify that the original was brilliant, and this should be, too.

Speaking of the original, Bastl had already delivered a deep 1.5 upgrade – impressively squeezing new life out of something so small.

Now, what they are not doing is offering support for user-installed upgrades in case you’ve got a Kastle and want to turn it into a Kastle Drum. (They even go as far as issuing a warning about that in their press release.) But I could imagine the user community can have some fun figuring that one out. And even better would be if someone worked out a way to make their own DIY hybrid of the two firmwares. Let me suggest that it be dubbed the Nathan Fillion. (Think about it.)

Kastle Drum is out now for MSRP 90 EUR before VAT (Europe), so just over $100 USD – and it’s available at noise.kitchen​ and ​synth stores worldwide​.


All things Kastle (Drum and original) are on GitHub:


Detailed walkthrough:

*Synthukkah Harry?