I am interested in how this mod was achieved @ akira^8GB. This is an awesome mod for the C64C Since I want to do some chiptune something like this is right up my alley

It's very simple, you just wire up some potentiometers to the correct pins on the controller ports. Both joy ports have 2 potentiometers (I think they're supposed to be 500KΩ each?), X and Y.  If you want to be a bit fancy, you can combine a potentiometer with some other components (caps, trimpot, resistors) to make a much nicer, linear effect with can be calibrated for zero deadzone:

http://chipmusic.org/forums/topic/4630/ … w-circuit/

For added fun, you can add a switching potentiometer that either grounds the audio in pin (it's left floating for some stupid reason and adds a shitload of noise as a result) or allows you to feed the audio output back into the audio input (through the potentiometer) to get a variable feedback effect. Which sounds really cool.