Earl (Fatha) Hines, 77, a pioneer of jazz piano playing and a legendary figure in American popular music, died April 22 in a hospital in Oakland, Calif., after a heart attack.

Through his "trumpet style" of playing the piano, Mr. Hines was credited with influencing either directly or indirectly almost every other jazz pianist since the 1920s.

A professional musician while in his teens, and an early associate of Louis Armstrong, Mr. Hines won renown in the entertainment world of the 1920s as the leader of his own big band in a famous Chicago ballroom.

In the 1960s and thereafter, he achieved new fame through recordings and personal appearance tours.

While many aspects of his playing made him popular with his audiences, it was Mr. Hines' musical inventiveness and his role as a keyboard style-setter that gave him his place in jazz history.

An influential figure among jazz pianists, Mr. Hines acknowledged the influence that Louis Armstrong had on him.

"I wanted to play the trumpet like him and he wanted to play piano like me, and we used to steal from each other," Mr. Hines once said.

In the late 1920s, while associated with Armstrong and drummer Zutty Singleton in Armstrong's Savoy Ballroom Five in Chicago, Mr. Hines perfected his "trumpet style" of piano playing.

It was a departure from the ragtime style that had previously held sway in the jazz piano arena, and in that style Mr. Hines, while still in his early 20s, made recordings with Armstrong that became classics.

"Nobody knew we were making history," Mr. Hines once said of those heady days. "We were just playing music."

One of three children in a musically gifted family, Earl Kenneth Hines was born in Duquesne, Pa., near Pittsburgh, on Dec. 28, 1905. His father played cornet and his mother played the organ and gave him his first piano lessons.

Although his mother wanted him to become a "serious" musician, his inclination was toward jazz, and by the age of 18 he was leading his own band in Pittsburgh. Then it was on to Chicago, and the formation of the band he led from 1928 to 1948. Among other things, the band was known as a cradle of bebop.

The group also helped set the style for the Big Band era and trained some of that era's top names, from vocalists Sarah Vaughan and Billy Eckstine to instrumentalists Dizzy Gillespie and Charlie Parker.

Mr. Hines' career seemed to slump in the late 1950s, but he was rediscovered and went on to new glory, which included a triumphant tour of the Soviet Union.

"Jazz is happiness," he said after the tour. "It's the language that makes everybody smile."

His marriage to the former Jane Moses ended in divorce. Two daughters predeceased him. Mr. Hines' survivors include one grandchild.