As a pub player, the sing along is my favorite element...I've found that and introduction to the tune...what it means, in a light way, helps people feel familar with the tune, and helps validates the need for them to join in. As an example: At a rather difficult pub, (recently opened) I was about to play the Irish Rover. Everybody had the words...(I pass out a booklet with my playlist) and the aire is pretty easy. Anyhoo, I introduced it as a tune about a ship that contained 4 million barrels of porter...and needless to say everyone on board was so locked and on the bollix that they sank the damn boat! Many laughed and loosed, as you say...but they also got some idea as to why it's an important tune, and fun too!