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 one singles, highlighted by "Physical," which spent ten weeks at number one in 1981-1982. Newton-John's sweet voice suited both country-pop and soft rock perfectly, which is what kept her at the top of the charts until the mid-'80s. After 1984, she was no longer able to reach the Top 40, partially because of shifting musical tastes and partially because she was unable to successfully record sexy dance-pop, no matter how hard she tried. Nevertheless, her '70s and '80s hits remained soft rock and adult contemporary staples into the '90s, when she was no longer recording frequently.