HOLLYWOOD, Oct. 18, 2000 -- Pop singer George Michael said today that he has purchased the Steinway piano used by John Lennon to compose "Imagine" for $2.1 million. "We can confirm that George Michael has bid successfully for John Lennon's piano," a spokeswoman for Michael told Reuters. "He decided to do this because the piano was a part of music history and because he wanted it to remain in Britain." The upright, walnut piano, which Lennon purchased in 1970 for some 1,000 pounds, went on the au