Not sure what is happening on your end, but all songs are submitted in mp3 format, and are downloadable in mp3 format.
If you click on the download button, and save it to your hard-drive, it is in the same format it was uploaded in.
The 'streaming' however is a totally different story.
All I can say is make sure you are downloading, and not streaming the file.
If that's still not working for you, give me more details, as in what errors you are specifically getting, etc., screen-shots of the whole procedure help as well.