Yet another sound piece up: “ReEno,” (MP3, 2.2MB) a collection of tweaked OS startup sounds blended into a 2.5-minute ambient sound comp. Inspiration loosely drawn from the tonal works of Wendy Carlos and Brian Eno. (Eno is said to have composed startup sounds for both Windows and Mac, though I can find no reference to his having composed the Mac chord.)
Update: Thanks, lupuS, for the quick tip. Yes, I found a MeFi thread where kindall mentions jazz guitarist Stanley Jordan composing the startup strum for earlier Macs, which was the basis for the fuller, richer startup chord we all know and love today.
Update: I was in error with this post; it seems that the Mac startup chord was done by Jim Reekes.