NASHVILLE, Tenn. — Eddy Arnold, whose mellow baritone on songs like “Make the World Go Away” made him one of the most successful country singers in history, died yesterday morning, days short of his 90th birthday.

Arnold died at a care facility near Nashville, a professor at Belmont University and author of the biography “Eddy Arnold: I’ll Hold You in My Heart,” Don Cusic, said. His wife of 66 years, Sally, had died in March, and in the same month, Arnold fell outside his home, injuring his hip.

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.

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.”