A new modular approach, using Cornish granite, CNC cut copper circuit boards and a lot of magnets.

Theory and rules:

Trying to give a voice to 370 million year old electronic components.
Changing/adjusting the crystal should have a clear result in most circumstances - they need to be in the centre of the circuit, so e.g. taking them away stops the sound.
Specially made cat's whiskers mounted in Cornish granite to make the minerals the focus of a live performance.
Incorporate 1920s crystal wireless technology.
No tuning.

Practice:

Single sided PCBs glued to neodymium magnets, so they can be rearranged inside a repurposed tool box (protects them during travelling/storage). Modular without (so many) patch cables, structure follows flow.
Extensive use of vactrols (LED/light dependent resistor). This is to make circuits simpler and be able to see what's going on at the same time.
Sequencing via simple building blocks, binary counters and shift registers.
Syncs with analogue synths via pulse train.
Works well with volca modular, which has become a standard addition in live gigs.
Inputs/outputs are signal, +4.5V, 0V, -4.5V. Other voltage ranges also work (the diode ladder filter needs at least this much to work). Signal is replaced by clock on the sequencing modules.

Modules

(Photo credit Nik Nenov (cc-by-sa))