Veteran country singer Slim Whitman has died of heart failure at the age of 90. The American star passed away at a hospital in Jacksonvillle, Florida on Wednesday (19Jun13). Known for his distinctive high-pitched yodel, Whitman enjoyed a string of hits during the 1950, '60s, and '70s, selling more than 120 million records worldwide. One of his biggest songs, 1955 track Rose Marie, was the longest reigning U.K. number one single for almost 40 years until the record was beaten in 1991. Whitman's fame faded but he continued to tour the world and record new music as recently as 2010, when he released his final album Twilight on the Trail. He was married to his wife Alma for 67 years prior to her death in 2009. The couple had a daughter Sharon, and a son Byron.