[math-fun] shuffling

Does the shuffle operation on in iPod choose a genuinely pseudorandom song from the playlist (so that, if there are n items, there's a 1/n chance that the next song will be the one you just heard)? Or does it pick the new song pseudorandomly from among the n-1 songs other than the one just heard? Or does it do something more interesting to make sure that a song isn't heard twice in too-close proximity? I only mention the iPod as one example, so if you happen to know about analogous "shuffle" operations on other platforms (and not just in the domain of music), I'd be interested. Jim P.S. I love having you guys around so I can get thoughtful and/or well-informed and/or fun answers to such questions five minutes after they occur to me!