The vocalists are trying to warn you that your house may burn down! You can't just insert a 30 amp breaker in place of a 15 amp one. The rating of the breaker depends on the wire that it feeds into. A 30 amp breaker has the same resistance as a 15 amp one and, unless you believe in magic, has no effect on the audio signal. Either breaker will deliver the current that your audio system demands, and you can't make the audio system demand more by changing the breaker.
The 30 amp breaker would permit you to plug in a TV and an Airconditioner as well as your audio system, and a few other things, without the breaker opening. The wires will get hot, and even if you don't start a fire right away the insulation of the wires will be damaged, which is a long-term hazard.