I don't think the "A Haskell tutorial" part of the submission title is accurate. It's an mp3 tutorial... which happens to use Haskell. Not everything which uses Haskell is specifically about doing so. :-)
Was that actually in the submission title here at HN? I didn't put that into it and it's not there now, so if it was.. we know an admin was fidgeting with it! :-)