But then I'm a drummer, so what do I know? I currently have a top line Roland electronic drum kit that I send those analog? signals to a small 60 watt amplifier if I don't want to use headphones.
You know all you need to understand that it was a con. The city council thought they could do it but it really is beyond the concept of sound engineering. Imagine trying to cancel the sound from your drums. Now if you pick one spot in the room, you may be able to do it there. But every place else some sound would exist that was not cancelled. So you woud need more speakers placed in all directions. and the sound engineer would need to adjust the level at each location to continue to cancel at every location. Finally the drummer would hit a louder or softer rip and everything would be out of adjustment again.
The answer? If it seems too good to be true, it probably is not true.