Having decided a particular sample from an mp3 would make a fun message alert on my phone I set about how to get said sample from the mp3.
Apparently Audacity is the answer...
[root@fatbeast ~]# yum install audacity
... at least it would be if it weren't for Fedora not supporting mp3s as policy, meaning the default Audacity package wasn't compiled with mp3 support...
[root@fatbeast ~]# yum remove audacity

A little judicious searching leads me to the Audacity-freeworld package which allegedly does include mp3 support.

[root@fatbeast ~]# yum install audacity-freeworld

A bit of fiddling and hey presto...sample extracted as mp3 for my phone!

At some point I'll add some instructions/screengrabs here if I remember!