James Myers, whose two-minute, eight-second tune “Rock Around the Clock” is considered the granddaddy of all rock ‘n’ roll songs, died of leukemia May 9 in Tampa, Fla. He was 81.

Myers wrote the song with Max Freedman in 1953. Bill Haley & His Comets recorded it in 1954, and the tune soared to the top of the charts in 1955 as the theme song of teen rebel movie “The Blackboard Jungle.”

With its rockabilly sound, the song was considered a breakthrough for crossing racial barriers by borrowing from rhythm and blues.

Myers, who also wrote under the name Jimmy DeKnight, wrote more than 300 songs and had bit parts in movies and TV shows, but “Rock Around the Clock” remained his most famous work.

He said the melody evolved in his head over a few years before he finally wrote it down. While picking out the tune on a piano at his office one day, his friend Freedman joined him.

“When we finished it he said, ‘What are you going to call it?’

I said, ‘Rock Around the Clock,’ ” Myers said in an interview with the Rockabilly Hall of Fame in Burns, Tenn.

“And he said, ‘Why rock? What’s that mean? Why not “Dance Around the Clock?’ ” And I said, ‘I just have a gut feeling.”

The song was No. 1 for eight weeks and went on to sell 22 million copies worldwide. It has been recorded by more than 500 artists, from Mae West to the Sex Pistols, and used in more than 40 movies.

A Philadelphia native, Myers was a drummer in his own band before joining the Army during WWII. After serving in the South Pacific, he returned to his home town to become a songwriter, country music promoter and music publisher.