Singer croons 'Valerie' but flubs lyrics at London show.By Mawuse Ziegbe Amy Winehouse performs with Mark Ronson July 6 in London Photo: Samir Hussein/ Getty Images Amy Winehouse surprised concertgoers in London on Tuesday night during a show with Back to Black producer Mark Ronson. The soul singer joined Ronson, who was fronting his new outfit Mark Ronson & the Business Intl, onstage for a cozy concert at the 100 Club, the BBC reports. The Grammy-winning singer hung out with Ronson throughout the latter half of the set while the producer debuted songs from his forthcoming album; however, the star only took to the mic during an encore.