"The neatest outcome would be that restaurants will . . . stop singing . . . songs."

IANAL, but I believe that particular practice is prohibited under the auspices of the Universal Declaration of Human Rights, which, while not legaly binding as such, forms the linguistic basis of legal constructs within binding covenants and treaties to which the United States is a signatory.

The fact that this practice continues should surely be pursued with the utmost priority by all those concerned with probity and justice among civilized peoples.