Much of Mr. Haggard’s cross-genre appeal was attributable to his versatile band, in which he sometimes played fiddle and lead guitar. But a great deal of it was also because of the pliancy of his singing voice, a deeply expressive instrument that lent itself to a variety of tempos, arrangements and emotions. He was as convincing singing about drinking and heartbreak as he was performing sentimental and devotional numbers, topical material and novelties.

Mr. Haggard was probably best known for his controversial hit “Okie From Muskogee,” a flippant broadside, released in 1969, that defended conservative heartland values against the hippie counterculture:

We don’t smoke marijuana in Muskogee

We don’t take our trips on LSD

We don’t burn our draft cards down on Main Street

We like living right and being free.

He later expressed ambivalence about the song’s message. To prove that he was more open-minded than “Okie” suggested, he had hoped to release “Irma Jackson,” a paean to interracial love, as a follow-up. Instead his record company issued “The Fightin’ Side of Me,” a jingoistic anthem that proved more divisive than its predecessor.

“I was dumb as a rock when I wrote ‘Okie From Muskogee,’ ” Mr. Haggard told the Americana music magazine No Depression in 2003. “I sing with a different intention now.”

Mr. Haggard wrote empathetically about poverty; the Great Depression was often his muse. His late-1960s hit “Hungry Eyes” revisited the dignity-starved lives his parents had led on arriving at California’s squalid Hoovervilles after fleeing the Dust Bowl in 1935:

A canvas-covered cabin in a crowded labor camp

Stands out in this memory I revive

’Cause my daddy raised a family there

With two hard-working hands

And tried to feed my mama’s hungry eyes.

Merle Ronald Haggard was born on April 6, 1937, in Oildale, Calif. His first years were spent in the abandoned boxcar that his father, James, a railroad carpenter, had converted into a home for his family. James Haggard died of a stroke in 1946, after which Mr. Haggard’s mother, the former Flossie Mae Harp, a strict and pious member of the ultraconservative Church of Christ, took a bookkeeping job to provide for her three children.