Ubuntu – Ubuntu 14.04 lockscreen turns off music + plays the ‘lock-sound’

Here is what xubuntu.org has to say about this:

[...] Currently, when locking, it is assumed you are either:

1. in a public space of sorts (the desktop at home hardly needs locking) and have walked away from the machine
2. using a system with more than one user

Stopping/pausing playback in both of these scenarios make sense.

However, this might be an annoying change for users used to having their music playback continue even when their session locks. If you don’t like this behavior, there are basically two solutions:

1. Set light-locker to lock the session “When the screensaver is deactivated”
2. Switch back to using xscreensaver
3. Add your user to the audio group on your computer and music playback will continue also with light-locker

The first option is a good workaround, because it means that your audio-playback will continue when the screen has been blanked. However, when you wake up your computer, e.g. by touching the mouse, it will pause the music until you log into your session again. The third solution is mentioned last, because it is not advised to add a user to the audio group (read The Audio Group wiki page for a comprehensive explanation). However, as long as you are on a single-user system, this might still be an option for you. [...]

Figure 1: Light-locker, by default, will lock out sound.

For those who choose workaround 2, here is how to remove light-locker and install good old xscreensaver:

sudo apt-get purge light-locker light-locker-settings
sudo apt-get install xscreensaver

After installation, a "Screensaver" icon will appear in the "Settings Manager" menu. Clicking it allows to configure xscreensaver.

Figure 2: XScreenSaver

I don't have gnome-screensaver installed, and the only command I can find that works is this:

dbus-send --type=method_call --dest=org.gnome.ScreenSaver /org/gnome/ScreenSaver org.gnome.ScreenSaver.Lock