Olivia Newton-John with Belinda Emmett

Olivia Newton-John skillfully made the transition from popular country-pop singer to popular mainstream soft rock singer, becoming one of the most successful vocalists of the '70s in the process. The transition itself wasn't much of a stretch -- her early-'70s hits "I Honestly Love You" and "Have You Never Been Mellow" were country only in the loosest sense -- yet the extent of her success in both fields was remarkable. As a country singer, her first five charting singles all went Top Ten in the U.S.; as a pop singer, she had no less than 15 Top Ten hits, including five number...