“It was kind of an instant connection.”

Jazz pianist and composer Jeremy Walker remembered the first time he performed with mezzo-soprano Clara Osowski. Walker had written some jazz-baroque fusion for Consortium Carissimi, a Twin Cities early music ensemble. Osowski was one of the soloists. And something just clicked during the 2016 project.

“We were talking after the show,” Walker remembered. “And I said ‘I’d love to write for you.’ ”

Osowski didn’t hesitate. “I loved the melodies Jeremy had written,” said the classically trained singer. “I was a saxophonist and had listened to a lot of jazz growing up.”

There was only one problem. “I was always terrified of improvisation,” Osowski confessed. “So I left the jazz world behind and thought, I’ll just sing what’s on the page.”

Yes, improvisation is second nature to jazz musicians like Walker, though many classical artists feel differently. These musicians may struggle with the gaps left by jazz composers. Walker struck a sensitive balance with “Haunted Blue,” the sequence of 13 songs he wrote specifically for Osowski. He provided the singer with definite melodic lines while leaving plenty of freedom in the piano accompaniment. Walker and Osowski will premiere the song cycle Sunday for an album release party at Dakota Jazz Club.

When Osowski first heard “Haunted Blue,” she immediately loved the music, she said. And yet she felt daunted by how little was written on the scores Walker provided. “I had nothing on the page except my vocal line,” she remembered. “So I had to stretch my ear a little bit for the new chord changes Jeremy uses every time we do these songs.”

When it came time to record “Haunted Blue,” Walker and Osowski were joined at the Twin Cities’ Essential Sessions Studios by local bassist Anthony Cox and tenor Tesfa Wondemagegnehu, who sang two duets with Osowski. Because most of Walker’s piano part was improvised, the album version of “Haunted Blue” is essentially a unique, unrepeatable performance of each song in the cycle.

“All the stuff on the recording is a complete take,” Walker clarified. “Each take of the same song varied quite a bit, and you couldn’t edit them together.”

“The songs are so different every time we do them,” Osowski added. “Which is why it’s so important that people hear them several different times.”

Neither and both

“Haunted Blue” was a departure for Walker, as well. The songs use texts by Walt Whitman, Henry Wadsworth Longfellow, Giovan Battista Marino and Minnesota lyricist Greg Foley. “I hadn’t written anything for what you might call the art song tradition before,” Walker said.

“The ‘blue’ in the title refers to the overall mood of the music,” he explained — its twilight world of rumination and reflection. “But it also refers to the type of harmonies I’m using. The ‘haunted’ part is like when you’re half asleep and half awake at night, and dreams combine with reality. The mood of the songs is deeper than I expected.”

So is “Haunted Blue” more jazz or classical? How should this new music be labeled?

“I hate labels,” was how Walker put it. “I grew up not knowing that jazz and classical were supposed to be that separate.

“But if the expression ‘jazz art song’ helps people to navigate some new territory, I guess I’m not averse to that.”

In any case, Walker didn’t give a thought to portioning the precise amount of “jazz” or “classical” while writing “Haunted Blue.” “They’re just songs to me,” he said. “And I’m really proud of the album.”

Nevertheless, a sense of risk-taking across musical boundaries will be Osowski’s abiding memory of the project. “Jeremy and I both have this language of our own worlds, and we’re both dipping our toes into each other’s world,” she said. “It was a really great conversation that doesn’t often happen in classical music.”

Terry Blain is a freelance classical music critic for the Star Tribune. Reach him at artsblain@gmail.com.