NASHVILLE (AP) — Country record producer and songwriter Billy Sherrill, who helped create the smooth "countrypolitan" sound of the 1960s and 1970s, has died. He was 78.

Sherrill's son-in-law, George Lale, said he died Tuesday in Nashville, Tennessee.

Sherrill's production style incorporated over-dubbing, strings and background vocals into country music to encourage crossover success for artists like Tammy Wynette, George Jones and Charlie Rich. He produced hits such as "Stand By Your Man," which he co-wrote with Wynette, "The Most Beautiful Girl," ''Behind Closed Doors," and "He Stopped Loving Her Today."

Born in Phil Campbell, Alabama, the son of an evangelical preacher, Sherrill played piano and sang starting in his childhood. He worked at Sun Records in Sam Philips' Nashville studio, and then joined the CBS record label in 1964. He won a Grammy Award for co-writing "Almost Persuaded," in 1966, which was a No. 1 hit for artist David Houston.

He was instrumental in signing Wynette, Barbara Mandrell and Janie Fricke to record deals. He also worked with Ronnie Milsap, Johnny Paycheck, Elvis Costello and Ray Charles.

"Billy Sherrill was the first producer to give me a push to start my own records, as he and CBS President Bruce Lundvall talked me into signing that first contract," Fricke said in a statement. "I was a busy backup singer and was not sure about going solo. I will hold dear those precious memories of magical studio productions with Billy, and will miss him greatly."

"He was an amazing producer of not only George but of many other artists," said Nancy Jones, George Jones' widow. "It is a sad day saying goodbye to such a wonderful man."