If you are new to the world of Linux audio it can be quite confusing as to how to get sound out of your machine. Unlike audio software that is self-contained, Linux applications tend to be a bit more specialized. Rather than having one program that is a sequencer, sampler, synthesizer, drum machine, amplifier, reverb unit, mixer and so on, each application in Linux tends to do one of these various jobs. So how do they all work together? That is where JACK comes in.
If this is your first time playing with PureDyne, the first thing to do is to go to the Audio menu and start up JACK Control. You'll see an interface that looks like this: