Sonic Pi needs jackd, the JACK audio connection kit daemon

The JACK audio connection kit is a sound server made for musicians.
When it works, it's great, but the default configuration fails for some
users.

If Sonic Pi fails to start for you, first try this:

- make sure you stopped Sonic Pi
- run qjackctl
- start the JACK daemon manually through qjackctl
- then start Sonic Pi again

While jackd is running, other sound applications using ALSA or
PulseAudio may be blocked. To avoid this while using PulseAudio, you
can install the package pulseaudio-module-jack and follow these guides
to set it up:

<http://jackaudio.org/faq/pulseaudio_and_jack.html>
<http://rivendell.tryphon.org/wiki/Debian_6_Setup_JACK2_with_Pulse_Audio>
<https://help.ubuntu.com/community/UbuntuStudio/ProAudioIntro/>
