Check out the crontab command.
crontab -e will open an editor with a sample file that allows you to schedule commands. There are command line MP3 player programs available that could be triggered from crontab. The next problem would be how do you switch it off / snooze it. I'm sure you'll be able to find plenty of information on connecting buttons to a Pi.
You'll want amplified speakers to stand a chance of waking anyone up too.
I don't have any noise from my Pi to wake me up, but My Pi does turn on the bedside lamp a few minutes before my alarm goes off. I use the Remote Control Socket thing from issue 8 of MagPi for that.