Mad keyboard

[Scarlett]

I have a Yamaha (piano) keyboard which is about 10 years old. Last night it was plugged in and turned on, and sudddenly this HORRENDOUS ROAR came from it- it sounded like very very distorted music coming from it. I have no idea how this could happen, as it is not connected to anything, and the demo does not sound like that!
Any ideas what was wrong? I had to unplug the power pack to get it to stop!

[naz_nomad]

Bad earth connection inside the keyboard

[Scarlett]

What does that mean, Naz? Is it dangerous?