Mai Cramer, the voice of the blues in Boston for 24 years, died of breast cancer on February 25.

She wasn’t a singer, but a radio host — of Blues After Hours, which aired every Friday and Saturday night on WGBH 89.7 FM. She’d been broadcasting the show since 1978.

Cramer was a bedrock blues traditionalist. That is, though her programming spanned generations and styles, her core repertoire was based on the postwar mother lode of Chicago electric blues — Muddy Waters, Howlin’ Wolf, Little Walter — as well as the immediately succeeding generation: James Cotton, Buddy Guy, Junior Wells, Luther Allison, Koko Taylor, and, of course, B.B. King. On any given weekend night, you might hear Stevie Ray Vaughan, Shemekia Copeland, Kenny Neal, or Lucky Peterson, but Cramer was bound to return to those progenitors. Names like Muddy, Wolf, and B.B. were as central to her aesthetic as surely as the names Monk, Miles, Mingus, and Coltrane are to the jazz modernist’s.

Cramer grew up in New York City, the daughter of a classical-pianist mother and jazz-fan father, discovered R&B on the radio, trolled the cut-out bins for blues records, and, as a teenager, saw acts such as Muddy Waters and the Temptations at the Apollo Theater in Harlem. Working as a filmmaker in Western Massachusetts in 1975, she got a slot on an upstart FM station simply because of her vast blues-record library. That gig eventually led to her work on WGBH.

Over the years, Cramer became the city’s chief blues proselytizer, traveling to festivals, conducting many on-air interviews with blues artists of local and international repute, and eventually putting up her own Web site — one of the first (www.realblues.com) — in 1995. In 1995, she also won a W.C. Handy "Keeping the Blues Alive" award.

Listeners came to Cramer for her humor, her depth of knowledge, the warmth of her delivery, and her obvious passion for the music. She was a free spirit, generous, boundlessly enthusiastic, and boundlessly supportive of blues musicians. When she showed up at the 1994 Newport Jazz Festival to introduce Buddy Guy, it was the 25th anniversary of Woodstock, and she proudly wore a Hog Farm bandana from the original concert. (The Woodstock anniversary concert was playing that very weekend, and Cramer was tempted to make a comment about it from the stage until friends warned her that Jazz Fest producer George Wein, still rankled by Woodstock’s competition, might not appreciate it.)

Cramer supported her blues habit with a variety of day jobs. She had worked at Digital Equipment Corporation for the past 10 years, held a PhD in education, and taught at Emerson, Northeastern, and Rhode Island College. She is survived by her husband, Peter Ward, of Melrose, and a sister, Carol, of New York. At press time, WGBH was scheduled to air tributes to Cramer in the morning and evening on Wednesday, February 27, and another, featuring music and interviews from artists she loved, on Friday, March 8, at 9 p.m. The date has yet to be announced for a live Cramer-tribute show at the House of Blues. A memorial service is scheduled for Saturday, March 30, from 2 to 4 p.m., at the Universalist Church, 70 West Emerson, in Melrose.