Add a beep to grub prompt

[vojtapolasek]

I think auditory notification of the fact that the boot menu appeared would be nice.
Unfortunately, this might not work on all hardware configurations, but it is worth trying.
It should be enough to add something like

GRUB_INIT_TUNE="2000 400 4 0 1 500 4 0 1 600 4 0 1 800 6"

into /etc/default/grub

There exists even a generator for tunes somewhere online.