A couple of days ago I learned a lesson about not cutting corners. I hadn't been bothering to use chip holders/sockets for the numerous multiplexer chips in the synth, reasoning that they have seemed fairly immune to damage in previous projects, and that I didn't have enough chip holders to hand anyway. After spending a few hours crafting my second module, I plugged it in and started testing. It worked to an extent, but was glitchy. After lots of confused troubleshooting, I eventually surmised that one of the chips was faulty. Not being particularly great at soldering/desoldering, this ended up being a bit of a pain. Luckily in this case I was able to sort the problem out using a slightly dirty hack, but all subsequent modules now feature chip holders. Here's a spot-the-difference photo:

In other news, I'm getting quicker and better at making the modules, which all feature a pretty similar design. I have also made some progress with repurposing the toy keyboard - more details soon.