Blue Note. The two words resonate in music theory as an ever-so-slightly flatted third in a chord that gives a tune its bluesy color, and, in recording history, as a record label that for decades set the standard for instrumental jazz.

From boogie woogie to bebop to hard-bop to soul-jazz to the New Thing, Blue Note’s blue-and-white label has stood for something distinctive and lasting since it was set up in 1939. Original LP copies now fetch astronomical sums, and the music on them forms a good deal of the bedrock for today’s jazz.

In recent years the focus of the label has shifted and broadened, with singers and singer-songwriters now dominating the featured new recordings on its website.

Blue Note’s evolution toward a singer-dominated label has been taking place for some time.

As early as 1993, jazz singer Cassandra Wilson was stretching Blue Note’s old boundaries, selecting material that would have once been considered hopelessly out of bounds (like the Monkees’ pop hit “Last Train to Clarksville”).

But it was a young singer-pianist-writer named Norah Jones — who suddenly hit it big in 2002 with her first Blue Note album, “Come Away With Me” — that accelerated the emphasis on singer-songwriters who now don’t have even a tenuous association with jazz.

And with Don Was — ace producer for Bob Dylan, the Rolling Stones, Bonnie Raitt and, most significantly, Willie Nelson — recently recruited as Blue Note’s chief creative officer, a job that involves signing and developing talent, the label’s move toward the pop mainstream would seem to be even more of a fait accompli.

While Was reveals a deep appreciation for Blue Note’s jazz tradition, the industry veteran, whose new position is his first as a label exec, says he wants to “serve the catalog and the spirit of the catalog, but not at the expense of discovering fresh talent.

“I think the essence of the Blue Note aesthetic transcends what scales or modes you’re playing in,” he says. “If you really distill those (classic jazz) records, they are people who are at the top of their creative form and their records almost capture them documentary style.”

But, he adds, “I don’t think we need to identify those scales as ‘jazz.’ I think you can broaden (the label) but I certainly wouldn’t want to give the impression that we’re abandoning jazz. I think it’s all music.”

Over the last decade, Blue Note signed veteran singers Al Green, Willie Nelson and briefly, Van Morrison — none of whom are thought of as jazz artists but who definitely display jazz-influenced bends and turns in their vocals.

The same could be said for Blue Note’s windfall with Jones. Amos Lee, spotted early by Jones and recruited for her opening act in 2004, brings a country-folk-rock sensibility to the table.

Singer/songwriter-multi-instrumentalist Priscilla Ahn, who uses her Korean mother’s last name professionally, has a wispy voice that resembles Jones yet her song base is strictly alternative pop. Keren Ann, of Russian-Jewish-Dutch-Javanese descent, combines folk with rock and electronica but like Ahn, her cool voice has the Jones quality that this label seems to gravitate towards.

And earlier this month, actor-singer-songwriter Jeff Bridges released his eponymous debut album on Blue Note/EMI, which, according to the L.A. Times, is less country in the manner of Bridges’ Oscar-winning turn as Bad Blake in “Crazy Heart” and “more beholden to the spirit of Tom Waits and Bob Dylan.”

There is also a “repertory players” aspect to the new Blue Note where various singers appear on their colleagues’ albums, which in its way upholds the tradition of the old Blue Note roster where top jazz musicians would play in each others’ recording bands.

Nelson and Blue Note trumpeter Wynton Marsalis — who has also been singing (and rapping!) lately — released “Two Men With the Blues” in 2008, and they hit it off sufficiently to put out “Here We Go Again” this year, with co-billed vocals by Jones.

In addition, Jones put in a guest appearance on Lee’s first album, and Nelson and Ahn guest on one track each of Lee’s latest, “Mission Bell.”

Jones’ latest, “… Featuring,” a compilation of duets from the last decade (including non-Blue Note sessions), establishes her as one of the most prolific collaborators, seemingly at home in all kinds of idioms.

“When that cross-pollinating happens, it’s something we love to encourage,” says VP of A&R Eli Wolf. “But it’s usually organic.”

Was appears to look forward while acknowledging the past, citing the label’s foundation figures Alfred Lion and Francis Wolff, and recording engineer Rudy Van Gelder, as establishing a tradition of artistic daring and audio excellence.

“If you listen to some of these records from the ’60s, you never heard anybody play the organ like Larry Young on ‘Unity’; and 10-15 years earlier you never heard anybody play the organ like Jimmy Smith,” he says. “Things that have become part of the musical vocabulary now are things that are taken for granted. They were the first, so I think it’s real important to record music that no one has ever heard before.

“I don’t want the label to simply become a museum based around the catalog. I don’t want to make new records that sound like 1960, I want to be part of creating some new music.”

Meanwhile, Blue Note’s current direction is paying off in the short term. “Two Men With the Blues” reached No. 20 on Billboard’s Top 200, Marsalis’ highest-charting recording by far. Lee’s “Mission Bell” went to No. 1 earlier this year and Jones’album sales have topped 40 million.

Blue Note still has some credibility with groups like the Jazz Journalists Assn., which named it 2011 Label of the Year.

On the other hand, jazz critic Scott Yanow, author of 10 books on jazz, wonders whether Blue Note will be hurt in the long run with its core audience. “Now one has to differentiate between the classic Blue Note label and the current label, which is barely significant at all to jazz despite the occasional jazz release,” says Yanow.

Yet for those who despair that a great instrumental tradition is being neglected, rising young trumpeter Ambrose Akinmusire’s recent debut on Blue Note, “When the Heart Emerges Glistening,” signaled the latest reawakening of jazz neo-classicism, while two new signings include saxophonist Ravi Coltrane and pianist Chano Dominguez (the latter signed by Bruce Lundvall, who as chairman emeritus, still keeps his hand in after stepping down as label chief last year). So perhaps Blue Note can have it both ways.

Was, for one, would like to bring back some of the pre-iTunes elements that made Blue Note the label of choice for serious listeners.

“There’s a difference between an album that someone records in sequence to tell a story, and downloading a file of Angry Birds,” he says laughing. “It’s incumbent upon us to be creative. And I don’t think it’s just a Blue Note issue. I think the nature of the music made by Blue Note lends itself to taking a leadership position in restoring value.”

Additional reporting by Steve Chagollan