The first is a background track that will continuously play whenever your prezi is viewed.
Alternatively, you can add sounds to specific path steps. These will begin to play only when you reach the chosen path step. They will stop playing when you move to the next path step.
Important Note: Currently, prezi supports the following audio file formats: MP3, M4A, FLAC, WMA, WAV, OGG, AAC, MP4, 3GP. For more information on which software applications you can use to create these kinds of files, click here.
Check out this video to learn how you can add sound to a prezi: