Lumberjack Fight is a circuit-bent Yamaha PSS-14 keyboard. It has switchable overdrive, a wide-range feedback control, and a retriggerable crash button. It also has a 1/4" output which can be plugged directly into a mixer or amplifier. It has been re-branded with scenes from a lumberjack fight comic.
If you want to try some of the bends, try the following:
The crash button simply shorts the two leads of the clock crystal. In my model, the clock crystal was a blue blob near the CPU. The feedback control feeds the output from the headphone jack to the input of the amplifier chip via a 100K potentiometer. I'm not sure which pin I used for the input, experiment and you are sure to find it. The distortion can be achieved by connecting the middle pin of the drive transistor closest to the CPU to various points via a 100K potentiometer.
Again, experiment here as my notes are not complete.