NASHVILLE, Tenn. (AP) — Eddy Arnold, whose mellow baritone made him one of the most successful country singers in history, died Thursday morning, days short of his 90th birthday.

Arnold died at a care facility near Nashville, said Don Cusic, a professor at Belmont University and author of the biography “Eddy Arnold: I’ll Hold You in My Heart.”

His wife of 66 years, Sally, had died in March, and that month, Arnold fell outside his home, injuring his hip.

Arnold’s vocals on songs such as the 1965 “Make the World Go Away,” one of his many No. 1 country hits and a top 10 hit on the pop charts, made him one of the most successful country singers in history.

Folksy yet sophisticated, he became a pioneer of “The Nashville Sound,” also called “countrypolitan,” a mixture of country and pop styles. His crossover success paved the way for later singers such as Kenny Rogers.

“I sing a little country, I sing a little pop and I sing a little folk, and it all goes together,” he said in 1970.

He was elected to the Country Music Hall of Fame in 1966. The following year he was the first person to receive the entertainer of the year award from the Country Music Association.

The reference book “Top Country Singles 1944-1993,”’ by Joel Whitburn, ranked Arnold the No. 1 country singer in terms of overall success on the Billboard country charts. It lists his first No. 1 hit as “What Is Life Without Love,” 1947, and for the following year ranks his “Bouquet of Roses” as the biggest country hit of the entire year.

Other hits included “Cattle Call,” “The Last Word in Lonesome Is Me,” “Anytime,” “Bouquet of Roses,” “What’s He Doing in My World?” “I Want to Go With You,” “Somebody Like Me,” “Lonely Again” and “Turn the World Around.”

Most of his hits were done in association with famed guitarist Chet Atkins, the producer on most of the recording sessions.

The late Dinah Shore once described his voice as like “warm butter and syrup being poured over wonderful buttermilk pancakes.”

Reflecting on his career, he said he never copied anyone.

“I really had an idea about how I wanted to sing from the very beginning,” he said.

He revitalized his career in the 1960s by adding strings, a controversial move for a country artist back then.

“I got to thinking, if I just took the same kind of songs I’d been singing and added violins to them, I’d have a new sound,” he told The Associated Press in 2002. “They cussed me, but the disc jockeys grabbed it. ... The artists began to say, ‘Aww, he’s left us.’ Then within a year, they were doing it!”