Well, I absolutely HATE 'jump ins' - went 2 one of these some long time ago in Stoke on Trent (uk) and this chap had a concertina and with his back to the crowd played all night without a break (I kid u not) until he went to the loo - when TWO of the crowd had a chance to sing. When he returned he seemed very surprised that someone was singing - but carried on playing again. As no-one said anything 2 him (no-one in charge) I told himto hos face that he had been the mistm selfish person I had ever come across at a club. He did not like it but then the truth always hurts.