Batch-reencode MP3s using a terminal tool.
this installs lame (http://lame.sourceforge.net/index.php), an MP3 enconder
sudo apt-get install lame
this reencodes all MP3s in the current folder to a bitrate of 32
for x in [ `ls -1 *.mp3` ]; do lame --preset 32 $x new32-${x}; done