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Of course, this isn't just any four-second clip. It's the sound — a soft da-dum, da-dumm, with a lush fade-out — that millions of computer users will hear every day, and perhaps thousands of times in total, when they turn on computers running Microsoft's forthcoming Windows Vista operating system.

To set the right tone — clean, simple, but with "some long-term legs," according to Microsoft's Steve Ball — the software maker recruited musician Robert Fripp.

Fripp, best known for his work with the '70s rock band King Crimson, recorded hours of his signature layered, guitar-driven sound for the project, under the close direction of Ball and others at Microsoft. Then, it was Ball's job to sort through those hours of live recordings to suss out just the right few seconds.

Fripp's involvement is not surprising. His occasional collaborator, Brian Eno, recorded sounds for Windows 95. Also, Ball, the Microsoft group program manager for WAVE — Windows Audio Visual Excellence — has in the past been Fripp's student and business partner.

Ball, a self-proclaimed renaissance man who is both an engineer and a musician, considered the work of about 10 musicians for the project. Some of those people were influential in the final four seconds as well.

Microsoft seriously debated several other sounds before settling on the final startup sound about three weeks ago. The rejects included a longer, lusher clip and a quick, techno-sounding piece. While many people liked an upbeat ditty with a clapping rhythm, it was eventually nixed for sounding too much like a commercial. Ball said the hand-clapping also seemed like too "human" a sound when paired with the new graphic for Vista.

"There's nothing that's especially human about our new Windows animation," he said.