Lou Donaldson, an alto saxophonist who became a bedrock of the jazz scene and whose soulful, blues-steeped presence in the music endured undiminished for three-quarters of a century, died on Saturday. He was 98.

His death was announced by his family. The announcement did not say where he died.

A mainstay of the Blue Note record label at the height of its influence and power, Mr. Donaldson recorded constantly as both a leader and a sideman beginning in 1952. He was a leading voice of the more elemental style that came to be called “hard bop,” an evolution out of the bebop revolution wrought by his inspiration on the alto sax, Charlie Parker. The National Endowment for the Arts named Mr. Donaldson a Jazz Master in 2012.

A player of impeccable technique, plangent tone, taste and refinement, Sweet Poppa Lou, as he was long known, nevertheless prized the raw gospel of Black church music and the gutbucket sound of rhythm and blues in his improvisations. The blues was at the heart of his sound: His album “Blues Walk,” released in 1958, is regarded as a jazz masterwork, and its title tune, which he wrote, became a jazz standard.

Mr. Donaldson also proved to be an acute talent scout for Blue Note’s owners, Alfred Lion and Francis Wolff, bringing to their attention both the young trumpet giant Clifford Brown and, later, the young guitar virtuoso Grant Green.

“I went down to Alfred Lion at Blue Note and gave him Clifford’s number,” he recalled in “A Wonderful Life,” his unpublished autobiography. “He brought him to New York and we made this tremendous date — tremendous date.”

Mr. Donaldson said he had also persuaded Mr. Lion to hand his close friend Horace Silver — the pianist and composer who would come to epitomize “the Blue Note sound” — his maiden recording date as a leader.