During normal operation or in Safe mode, your computer may play "Fur Elise" or "It's a Small, Small World" seemingly at random. This is an indication sent to the PC speaker from the computer's BIOS that the CPU fan is failing or has failed, or that the power supply voltages have drifted out of tolerance. This is a design feature of a detection circuit and system BIOSes developed by Award/Unicore from 1997 on.
What the fuck? Not exactly intuitive is it?
"Oh my god, it the haunting strains of Beethoven's Für Elise, what can it mean? Oh, I know: it must mean that my CPU's fan is knackered! Thank you,