The Microsoft Sound composed by Brian Eno.

In 1994 Microsoft corporation designers Mark Malamud and Erik Gavriluk approached Brian Eno to compose music for the Windows 95 project. The result was the six-second start-up music-sound of the Windows 95 operating system, The Microsoft Sound (.wav). In the San Francisco Chronicle he said:

"The idea came up at the time when I was completely bereft of ideas. I'd been working on my own music for a while and was quite lost, actually. And I really appreciated someone coming along and saying, "Here's a specific problem — solve it."
The thing from the agency said, "We want a piece of music that is inspiring, universal, blah- blah, da-da-da, optimistic, futuristic, sentimental, emotional," this whole list of adjectives, and then at the bottom it said "and it must be 31/4 seconds long."

Talking about a proposal for a sound work which could be installed in an airport "when you're changing planes and you're and you've got an hour to spare and you don't want to spend more money on calculators."