Any popular tune that the majority of people can sing.
Any tune with a simple melody and easy words that the audience can learn to sing in an instant.

You probably will have no success to have 'em sing along the "Auctioneer" or "El Paso", but "Hey Li Lee Li Lee" will work.

A lot of Christmas season songs will work, probably not suitable to use any other time of the year. (You could, if you dare to, and might even have a lot of success on a very hot summer day with "Jingle Bells" for example.)

Know your crowd and you might have success with Metallica's "Nothing Else Matters"
In an Irish pub many Irish songs will work so well that you don't even have to sing.

So, actually it all depends on the crowd and the crowd's knowledge of songs.


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