April 6 (Reuters): Country musician Merle Haggard, who emerged from prison to become the poetic voice of the working man with hits such as Mama Tried and If We Make It Through December, died today, his 79th birthday, said manager Frank Mull.

The country legend had cancelled all his concerts for the month of April due to illness.

Haggard's repertoire included songs with traditional country music themes such as drinking and heartache but he also infused them with more insight and tenderness than most honky-tonkers. He also broadened the genre by writing about poverty, loneliness and social issues.

Haggard once said he preferred playing guitar to singing but it was his voice that made him stand out.

"Haggard's exceptionally true intonation, his command of varied vocal textures and his insinuating phrasing would make him a superior vocalist in any idiom," The New York Times said of Haggard in his prime. "Like Muddy Waters in the blues field and only a handful of other performers, he both embodies and transcends his rich American musical heritage."

Haggard's sound drew from traditional country but also touched on folk, pop, jazz, blues and rock and his songs were covered by the likes of the Grateful Dead, Elvis Costello and Lynyrd Skynyrd.

"I can't remember when I haven't listened to him," said Rolling Stones guitarist Keith Richards.