by Vera H-C Chan Oh no they didn't. Oh yes, they did, did, didgeridoo. The Top 9's theme on " American Idol " was the Lennon - McCartney songbook, but the reality show looked more like a world music concert with some unusual pipes. Judges' fave Crystal Bowersox took to her guitar to sing " Come Together ," but got musical accompaniment by a gent tooting a four-foot-long didgeridoo . The instrument mash-up didn't end there. In the anchor spot,