Use the volume knob on your USB keyboard with Quartz Composer compositions via the HID Input patch included with QC.
Choose your keyboard from the list of devices. The Dell Windows keyboard I’m working with shows up as two different devices: Generic Desktop Keyboard and Consumer Control. I chose the latter and found which of the outputs had some activity when turning the knob. The knob is a rotary encoder, not a potentiometer, so you shouldn’t expect to see a continuously changing value. The value is .5 when you’re not turning the knob. When turning left, the value momentarily changes to a number less than .5. Turning to the right makes the value go over .5. Here is an example composition that controls a counter with the knob.
