This Grub Init Tune will make your computer sound like a Super Mushroom every time you turn it on! This only works for the Grub bootloader - this generally means you need to have Linux (or other Grub-based OS) installed.
Here's the code, which goes in your /etc/default/grub file:
GRUB_INIT_TUNE="1750 523 1 392 1 523 1 659 1 784 1 1047 1 784 1 415 1 523 1 622 1 831 1 622 1 831 1 1046 1 1244 1 1661 1 1244 1 466 1 587 1 698 1 932 1 1195 1 1397 1 1865 1 1397 1"