Here's an answer minus several glasses of wine!
In terms of 'how', if it was something that somebody wanted to do then I think that iTunes on 'random' might be the easiest way to do it. Otherwise it might be down to something like using Doug Dawson's XML sound gauges to activate a sound file on startup, but it would need some kind of trigger early on in the startup process, and I can't think how you might activate that.
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