I've always been surprised some inspired performance artist hasn't done this to the live sound feed at a big music festival like Bonnaroo or Coachella yet. Audio runs from the stage/band to a sound guy in the middle of the field who controls the mix then from there it goes back across the field to the PA system mounted on stage. The audio cables are literally just big snakes that run right through the crowd where anyone could access them. Highjack a post mixer cable and bob's your uncle.
The only hitch would be that afaik at festivals the pa arrays are passive so you'd need to steal power too so you can power an amplifier and send a powered signal, but if you managed that it'd be even worse than the tv broadcast intrusion because there's no easy way to shut it off, the sound guy has no control because you're after him in the signal chain and nobody onstage is set up to handle something like that. It's not like beyonce is gonna climb the scaffolding and start unplugging speakers when the crab rave starts playing inexplicably.
The only hitch would be that afaik at festivals the pa arrays are passive so you'd need to steal power too so you can power an amplifier and send a powered signal, but if you managed that it'd be even worse than the tv broadcast intrusion because there's no easy way to shut it off, the sound guy has no control because you're after him in the signal chain and nobody onstage is set up to handle something like that. It's not like beyonce is gonna climb the scaffolding and start unplugging speakers when the crab rave starts playing inexplicably.