It's known as '60-cycle' hum, and is indeed a grounding problem. I don't
think it's dangerous, and there are a couple of ways to defeat it. The
first would only work if the guitar has two pickups, but reversing one of
them electrically will render the hum impossible (the theory behind
'humbucking' pickups). The next is to simply reverse the plug in the
outlet, which will get you back in phase.

This was the scourge of many a garage band years ago, but as you've noticed,
your daughter's touch gets things right back in phase. She won't get
electrocuted at the guitar either, because it's passive. The problem is at
the amp, and it's annoying rather than dangerous.

Keith

"Remi" wrote in message
. 76...
We just moved into a 60 year old house and discovered that my daughter's
electric guitar and amplifier won't work properly. There'a a loud hum
coming from the amplifier. It stops when she puts her hands over the
strings, but starts up as soon as she removes her hands. Could this be a
grounding problem? Any suggestions? (There's nothing wrong with the guitar
or the amplifier. She also has a bass guitar and a bass amplifier and the
same problem is occuring with them too). Thanks.