LiveSPICE is a SPICE-like circuit simulation tool for processing live audio signals. The motivation for developing LiveSPICE is to help prototype guitar effects and amplifiers, without requiring constructing a physical circuit or waiting for an offline simulation to run to try it out. With LiveSPICE, you can design the circuit in an easy to use visual schematic editor, and simulate it using your real instruments as input signals and your speakers as the output, in real time.
The main website for downloads, documentation, and other information about LiveSPICE is www.livespice.org.
LiveSPICE is a tool that I've wanted for a while now. I couldn't find any existing SPICE simulators with this feature, and I thought this would be a really fun project. It proved to be a bit more difficult than I expected, I was stumped for nearly a full year on some of the numerical simulation issues. There is still a lot of room for improvement, but it now is quite usable and has a decent library of components to use.
There are not one, but two GitHub repos associated with this project: