On Aug. 10, 1920, two African-American musicians, Mamie Smith and Perry Bradford, went into a New York studio and changed the course of music history. Ms. Smith, then a modestly successful singer from Cincinnati who had made only one other record, a sultry ballad that fizzled in the marketplace, recorded a new song by Mr. Bradford called “Crazy Blues.” A boisterous cry of outrage by a woman driven mad by mistreatment, the song spoke with urgency and fire to Black listeners across the country who had been ravaged by the abuses of race-hate groups, the police and military forces in the preceding year — the notorious “Red Summer” of 1919.

“Crazy Blues” became a hit record of unmatched proportions and profound impact. Within a month of its release, it sold some 75,000 copies and would be reported to sell more than two million over time. It established the blues as a popular art and prepared the way for a century of Black expression in the fiery core of American music.

As a record, something made for private listening in the home, “Crazy Blues” was able to say things rarely heard in public performances. Seemingly a song about a woman whose man has left her, it reveals itself, on close listening, to be a song about a woman moved to kill her abusive partner. As a work of blues, it used the language of domestic strife to tell a story of violence and subjugation that Black Americans also knew outside the home, in a world of white oppression. The blues worked on multiple levels simultaneously and partly in code, with “my man” or “the man” translatable as “the white man” or “white people.”

Ms. Smith, a skilled contralto with a keen sense of drama, brought clarity and panache to words that would strike today’s listeners as conventional only because they have been replicated and emulated in countless variations over the past century: “I can’t sleep at night/ I can’t eat a bite/ ’Cause the man I love/ he don’t treat me right.”

Out of her mind with despair, the singer turns to violence against her oppressor for relief in the chorus that gives the song its title: “Now the doctor’s gonna do all that he can/ But what you’re gonna need is an undertaker man/ I ain’t had nothin’ but bad news/ Now I’ve got the crazy blues.”

That a woman was singing made the song an acutely potent message of protest against the forces of authority, be they male or white, domestic or sociopolitical.