By GEORGINA LITTLEJOHN Mocking: Katy Perry sang an acoustic and tuneless version of Rebecca Black's Friday on stage in Melbourne last nightThere are probably a lot of teenage girls who would be thrilled to bits if Katy Perry decided to sing one of their songs during her concert.But not Rebecca Black, who will no doubt be feeling a little disappointed with the Firework star's 'tribute' to her. Perry poked fun at the teenager when she performed her song 'Friday' at her gig in Melbourne yesterday. You know the words: With a sarcastic look on her face, Katy led the audience into a rendition of the chorus And Katy decided the only way to sing it was out of tune, mocking the fact that the 13-year-old used auto-tuning on her vocals.As she started an acoustic set during the gig, Katy, 25, with a mocking wide-eyed look on her face, declared to the crowd: 'So I can't play the flute. But that's ok. Because everything magical happens on a Friday.'She received loud cheers from the audience inside the Rod Laver Arena, with one, who was recording the performance, declaring: 'No way'. Big Down Under: Rebecca Black, seen here arriving at LAX airport yesterday, had 15,000 Melbourne fans singing her songRebecca Black, who comes from California, shot to fame earlier this year after heavily auto-tuned video of Friday went viral.But unfortunately for the teen, it attracted a barrage of criticism and even death threats after her video was viewed by more than 110 million times on YouTube. And Black admitted she was shaken by the vicious comments she received online.Speaking on Good Morning America last month, she said: 'When I first saw all these nasty comments I did cry. I felt like this was my fault and I shouldn't have done this and this is all because of me. Now I don't feel that way.'Katy Perry singing Rebecca Black's Friday source: dailymail
