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I use qsynth to output sound from my MIDI keyboard. That part works great, and the MIDI keyboard sounds great.

However, once that MIDI keyboard is connected, my computer immediately becomes unable to output ANY sounds other than sounds from the MIDI keyboard, and this continues until I reboot the computer, even if I stop and close both qsynth and qjackctl.

I have no idea what's causing this, but I find it really annoying. How can I stop it from happening?

My Ubuntu version is 13.04 (Raring) and I have qsynth 0.3.6 and qjackctl 0.3.9. My system uses pulseaudio 1:3.0-0ubuntu6 to output sound, which I've heard has some problems but I'm not sure if this is one of them.

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  • alsamixer? qjackctl could be a possibility as well.
    – Wilf
    Nov 28, 2013 at 19:29

1 Answer 1

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If you're using jack to route your audio, then the jack server will take exclusive control of your sound devices, thus making pulseaudio unable to output any audio for other applications.

This is what you want when using low-latency audio, as pulseaudio isn't designed for low-latency work. However (as you've noticed), it means that when you're done, pulse isn't able to output any more sounds.

The solution should be to stop the jack server when you're done with qsynth, so that the sound devices are available to pulseaudio again. The 'Stop' button on the qjackctl main UI should do this for you.

You may also need to quit and restart pulse after doing this; use can use pactl to exit the pulse daemon:

pactl exit

- and the daemon should automatically restart when you next play audio.

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  • I'd like to add now that I have this all sorted out that if you use KXStudio Cadence to control JACK, it comes with a pulseaudio bridge which allows you to route all your sound into JACK. You may sometimes have to restart pulseaudio while using it to get the sound to actually output through the bridge because pulse is weird like that, but it pretty well solves the problem when you want to have regular sound for whatever reason but don't want to disturb JACK.
    – Takumi
    Jan 2, 2015 at 2:55

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