Non-working sound in a legacy apps like tvtime which rely on OSS is a common problem these days. The easiest way to fix it is to install the alsa-oss compatibility package and add yourself to the 'audio' group:
$ sudo aptitude install alsa-oss $ sudo usermod -G audio `whoami`
After doing that either re-login (or at least open new shell) and check the output of the 'id' command - it should contain 'audio'.
Sometimes after doing that you'll have mute working, but still no volume adjustment. If so, simply specify the correct mixer channel in your tvtime config:
<option name="MixerDevice" value="/dev/mixer:line"/>
One may need to use 'pcm' or 'vol' insteam of 'line'.