Thank you both for your suggestions. Having experimented further, I find that, as I expected, the earpieces are completely inaudible when they are not in my ear (they are just the little ear-bud type of thing). The default connections shown bu aJackCtl are: System(capture) to qTractor and PulseAudio JACK Source qTractor and PulseAudio JACK Sink to System(playback) This seems about right, to me, I experimented with removing the connections to/from PulseAudio, but this doesn't make any difference to the problem I have been getting. I also experimented with muting various things in Pavu, without any success. So either I am doing something very basic completely wrongly (quite likely!), or perhaps there is some sort of crossover going on in my sound card between input and output. I did attempt to repeat my experimental recording on my desktop computer, but couldn't figure out how to get the input from my webcam's microphone into qTractor. When I start Jack, the System(capture) node doesn't appear in the connections graph at all. David