There have been various iterations of synths built that work with natural semiconductors.

Version 1: the cardboard crystal synth

This one is built from cardboard boxes using springs and wires to build different circuits. Designed to be used in workshops with families and a wide range of ages of children, it comes with a booklet with example circuits, ranging from lighting the LED to test the battery, making a simple sound to more complex sounds and integrating crystals (collected as part of the workshop) with the built in holder and cat's whisker. It comes with it's own amplifier and speaker, and the can get pretty loud (especially when ten of them are in use at once).

For more information see the Cardboard synth page.

Version 2: the log synth

This version was designed as a simpler way to get sounds working in the workshops during 2025. You can add three crystals that are used in three different voice circuits, a noise generator, a triangle/sawtooth oscillator (includes frequency modulation) and a square wave frequency modulation voice. Each of these voices are filtered so you can tune into more interesting aspects of the sounds, and remove the harsh aspects - predominant in the cardboard version. These signals can also be gated and modulated via simple sequencers that can be clocked to external hardware. It was then possible to create more beat based techno music.

For more information see the Log synth page.

Version 3: the granite synth

This version is designed from the successful circuits of the log synth, but can be manufactured a bit more simply - and with increased stability from using blocks of (Cornish) granite to make it easier to tweak cat's whiskers on the synths. These are still in the process of design, but are modular - so e.g. different filters can be swapped in and out. Circuit boards are created using CNC milling on single sided copper boards and surface mount components are used to reduce costs and size. The use of raw copper and granite are chosen to match with the crystal material, coming from metal ores formed due to the presence of the granite.

For more information see the Granite synth page.