It is hard to understand why PowerPoint never implemented this, but if you ever had to play a sound or music during a presentation, you had to peg the start of the audio to a particular slide, and once the audio starts there’s no easy way to stop.
Completely cumbersome if, say, the first time you teach some children to sing along a set of slides. You can’t skip forward to show a slide without activating the music; you can’t go back to the first slide without restarting the music; you can’t stop the music if you realise the kids need a bit more time to follow.
Mega Soundboard is the easiest and best answer to this problem. Its taken a long time for me to find this; none of the other soundboards, or hotkey solutions, or full featured media players (e.g. VLC, fubar2000) does this as simply and as elegantly as Tom4nt’s Mega Soundboard: you setup your selection of audio files, assign each a hotkey (which are global), and you just press the hotkey to play the desired audio without the program needing to be in focus (i.e. you need PowerPoint to be in focus to control the slides).
A start/stop global hotkey can be assigned as well to stop the audio at will.
Voila! Its open source to boot as well!