Teena Marie, 54, the Grammy-nominated R&B performer and perennial concert favorite, died in her sleep Sunday at her California home.

According to her publicist, Lynn Jeter, a month ago the singer-songwriter-producer suffered a grand mal seizure, a neurological event marked by a loss of consciousness and violent muscle contractions.

"Luckily, someone was there," Jeter told CNN. "The ambulance took her to the hospital, and on the way she had another seizure." She had been believed to be feeling better, however, and was preparing for a show this week in Atlanta when her daughter, Alia Rose (the singer Rose Le Beau), found her Sunday.

Born Mary Christine Brockert in Santa Monica, Calif., Marie initially shot to stardom as a protégé of the funk legend Rick James, who wrote all but two of the six songs on her 1979 debut for Motown Records, Wild and Peaceful. Label honcho Berry Gordy Jr., suspecting soul audiences at the time might reject the budding ingenue if they knew she was white, chose not to include a picture of her on the cover.

Yet Marie, also known to fans as Lady T (after her 1980 album of the same name), was among the first non-African American artists routinely to chart high on the R&B charts, something that has become more common in this era of Christina Aguilera, Justin Timberlake, and Robin Thicke. Indeed, Marie's synthed-up sound served a crucial role in the development of modern urban-soul.

"Teena was a black voice trapped in a white body," Cathy Hughes, founder of Radio One, told CNN. "I would always tell her that she was one of the greatest vocalists of our time."

By the end of the '80s, having topped the R&B countdown with "Ooo La La La" and nearly done the same on Billboard's all-inclusive pop chart with the 1984 smash "Lovergirl," which reached No. 4, the sexpot-with-chops had helped pave the way for the likes of both lasting pop icons like Madonna and Cyndi Lauper as well as a host of also-rans (Klymaxx, Exposé, the Mary Jane Girls).

With her third disc, Irons in the Fire (also from 1980), Marie, already adept at guitar and keyboards, began to write and produce her albums herself, scoring again with "Portuguese Love" from 1981's It Must Be Magic.

The next year, she wound up in a heated legal battle with Gordy over her contract and disagreements regarding releasing new material. She sued the label, and the eventual result was what's called "the Brockert Initiative," also known as "the Teena Marie Law," which made it illegal for a record company to keep an artist under contract without issuing new material. Artists held back by such behavior would be able to sign and release with another label.

"It wasn't something I set out to do," she said of the ruling at the time. "I just wanted to get away from Motown and have a good life. But it helped a lot of people, like Luther Vandross and the Mary Jane Girls and a lot of different artists, to be able to get out of their contracts."

She would go on to record for various labels, including Epic, Cash Money Classics, and famed Southern haven Stax, which issued her lengthy, guest-laden final album, Congo Square, in June 2009. Marie eventually racked up four Grammy nominations but never scored a win.

Friends and collaborators were quick to offer condolences.

"The enduring influence of Teena's inspirational, trailblazing career could only have been made possible through her brilliant songwriting, showmanship, and high-energy passion, which laid the groundwork for the future generations of R&B, hip-hop and soul," said Concord Music Group chief label officer Gene Rumsey, whose empire oversees Stax. "We feel extremely fortunate to have worked with a visionary who changed music in indelible ways."

"We're shocked and deeply saddened by the sudden loss of Teena Marie," legendary Philly soul producers Kenny Gamble and Leon Huff said in a statement. "She was one of the most memorable, soulful, and unique R&B vocalists to come out of Motown."

Eddie Levert, cofounder of the O'Jays, praised her both as a singer and mother. "There are a lot of black people who swore by her and believed in her as far as her music was concerned," he told CNN's Roland Martin. "She was a good mom, and to me that is saying a lot."