Question 391: Why the loud Wallume?

A Sunday Times article about amongst the most well known bands in the world, it goes on to label them for who they were, instead of the error printed before it.

"At the launching of the new magazine IT the other night a pop group called the ___X____ played throbbing music while a series of bizarre coloured shapes flashed on a huge screen behind them. Someone had made a mountain of jelly which people ate at midnight and another person had parked his motorbike in the middle of the room. All apparently very ___Y_____."

Questions:
1) ID X and Y