Lady Sings the Muse : What began as a lark is now a deep commitment and source of inspiration for Madeline Eastman.

When she was 18, Madeline Eastman thought, “Well, maybe I’ll be a jazz singer.” She’d seen the 1972 picture “Lady Sings the Blues,” in which Diana Ross plays Billie Holiday, and had fallen in love with the music.

Singing might be a lark; that was the way Eastman saw it then. Now, at 40, she knows what a major commitment singing is. “It’s a lifetime of work, if you’re serious about it. And I am . . . deadly serious.”

Asked why she’s so devoted to her craft, the vocalist, who appears Thursday at Legends of Hollywood, rattles off a list of affectionate reasons with the same speed and spirit she might use to handle a jack rabbit up-tempo tune from her recent “Art Attack” CD.

“I love to sing, the art form of singing,” she begins in a phone conversation from her home in San Francisco, where she lives with her husband, the noted drummer Vince Lateano. “I love to express myself. Singing taps into every part of my being: my intellect, my artistic side.

“You have to be really smart, because you’re creating on the spot, flying by the seat of your pants, making something beautiful. Singing is very worldly. You end up playing and interacting with people that you never would, both musicians and audience members. It leaves no stone unturned. It’s a rush.”

Not just jazz but the lifestyle that goes along with it appeals to Eastman. In the past two years, she has been going beyond the clubs in her native San Francisco, where she has established a solid home base, to work such top U. S. jazz rooms as the Blue Note in New York, Blues Alley in Washington, D.C., Scullers in Boston and Jazz Alley in Seattle.

“I love being around creative people and being involved with something where the learning process is unending,” she says. “No matter how good you get, there’s more to learn. I feel stimulated every day by music.”

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Even the business side of jazz has given Eastman a charge, except “when I’ve had to grovel,” she says, adding one of her throaty, distinctive laughs. And while she says it’s been fun to map out a career, understanding how to get from one stage to another, she’s ready for a manager.

“I book myself, for the most part, and it’s getting tiresome,” she says. “It takes so much energy to do the business side. I wish I could just sing and let somebody else do it.”

At Legends, where she’ll appear with pianist Tom Garvin, bassist Tom Warrington and Lateano on drums, she’ll offer tunes from her three self-produced albums on Mad-Kat records, a label she owns with fellow-San Francisco Bay Area singer Kitty Margolis. Among her potential selections are a jaunty version of “Gypsy in My Soul,” Thelonious Monk’s “Evidence,” to which she’s written lyrics, and classic pop standards such as “My Heart Stood Still.”

Eastman says her method of delivering a song’s meaning is to get inside it.

“First of all, I really think about what I sing before I sing it,” she says. “Basically, my forte is communicating the lyrics. It boils down to how you phrase a song so it’s believable or not believable. It’s about allowing yourself to be intimate with a song, stripping it down to its emotional core, not using a bunch of fancy singer tricks.

“In this area, I’m a big fan of the late Carmen McRae’s. She’s the ultimate interpreter of lyrics. Her phrasing is so hip. She groups words together so they make sense, rather than being strictly true to what’s written on the page. Therefore, there’s a freedom in her singing that’s a joy to listen to.”

Many fans and critics feel the same way about Eastman. One is Boston-based writer Fred Bouchard, who, in the January issue of CD Review magazine, reviewing “Art Attack,” said, “Eastman’s songs are far from broke, but she fixes them anyway with a savvy alto and a sharp rethinking.”

Eastman calls herself a jazz singer not because she scats, but because she improvises with the lyrics.

“I’ll take a second chorus, using the words but changing the melody under them, changing the rhythm,” she says. A self-described “work in progress,” Eastman says she’s a much better singer now than ever before, mainly because she can really enjoy what she’s doing.

“I used to have terrible stage fright. I had to sing with my eyes closed,” she says. “But about seven years ago, though singing was just as important to me as ever, I learned to lighten up and enjoy the experience of it. That was a major breakthrough. I could sort of open up and put the music out there instead of having the feeling be internal. It was because I was getting older. Age and experience made the difference.”

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WHERE AND WHEN

What: Madeline Eastman sings at Legends of Hollywood.

Location: 11720 Ventura Blvd., Studio City.

Hours: 8:30 p.m. to 12:30 a.m., Thursday.

Price: $7 cover ($5 with student ID), two-drink minimum.

Call: (818) 760-6631.