I've decided to make some modifications to the Simple Mp3 Bar module for Joomla 1.5. Simple MP3 Bar - version 1.1, now allows you to choose whether you want to play one song or a group of songs as a playlist (not xml).
To make a playlist all you have to do is select playlist, type the names of the files (eg: love-song.mp3, peopleperson.mp3, partytime.mp3), the respective names and poof!!! Your playlist is created.
It's one of the simplest mp3 players you'll find for Joomla 1.5.