"We are talking about people who are exercising a right to perform in a public space"

Wait a minute. What do you mean by 'public space.' Anybody's space? That is not the case. That park is paid for by somebody, probably the taxpayers of the city or county. It is THEIR park.

It was voted for by the people for their enjoyment and edification. Having to walk through it while one person plays in Eb and the next person plays in A, all however loudly they wish, is not what they had in mind.

Read the rules. They are fair and reasonable. Even given the rules, it sounds like hell, based on Deckman's description. You will not find me, a person with keen hearing, anywhere near it.