i agree this is getting worse over the past decade
my best solution is
1) wait until the song is finished
lean over and tap on the shoulder and say
for singers:
"im sorry..but I cannot hear the actors singing over your singing
Could you please respect the people around you and not sing during the performance?"
for eaters
Im sorry, but i cannot hear the actors over the rustling of your food. can you please respect the people around you and not eat during the performance?
for talkers
Im sorry, I cant hear the actors over your talking....
etc
This actually WORKS 90% of the time
the other 10% when they dont stop or escalate
i got up and got the manager
Using a kind and sincere tone and direct eye contact really makes all the difference
With how much i love musicals and how much time effort and money it takes to get to nyc to see my favorite shows, i absolutely refuse to let someone ruin my experience.....
manypeople are not regular theatre goers and do not know common etiquette
I agree that no food or drink should be allowed in the theatre
I believe anyone using a camera gets one warning from ushers, and get ejected the second time
I wish theatres would read a few more house rules to the audience before each performance
I really empathize withe op and anyone who has had to put up with having a show experience diminished by another patron.....