Music and Sound
The following sound is PERMANENTLY banned:

Different methods of music and sound:
where to get sound
Where to find pre-recorded sound effects and music in Scratch:
There are heaps, you simply have to listen to them (on your headphones):

You can also record a sound (like a voiceover for example). If you want to record, do this at home:

Finally you can upload an existing mp3 or wav file sound:

questions
Compose your own 'background music'. I've gone for something suspenseful.. it sounds terrible: