Very bad idea in my opinion.
I also believe it would be a violation of 110.7
110.7 Insulation Integrity.
Completed wiring installations shall be free from short circuits and from grounds other than as required or permitted in Article 250.
It is very likely along with tripping the branch breaker you will trip a main putting people in the dark.
A handle tie will not always trip the other breaker, it is not intended to do that.
There are so many better ways to cut off a sound system. If I am not mistaken you can actually damage speakers by dropping the power out in the wrong order.
[This message has been edited by iwire (edited 04-30-2005).]