Gustav Mahler is invited to rant from beyond the grave.

Among the five new pieces being premiered by Dolce Suono Ensemble on Wednesday as part of its Mahler 100/Schoenberg 60 Project, one of Mahler's letters is being set to music by Princeton-based composer Steve Mackey.

Titled "Herr Guttmann," the piece has opera bass Eric Owens as the voice of Mahler threatening to walk out on the premiere of his own Symphony No. 8 for lack of rehearsals. Herr Guttmann, the impresario, believes the chorus' enthusiasm will get it through. Mahler disagrees, adding that if the singers are forced to rehearse on the day of the concert, "they're all going to die."

You hear Mahler's existential longing in a melody quoted from the Symphony No. 8, but from there, it's "snarky Mackey," said the composer, whose roots are American popular music and give Mahler's resignation threats an element of rock-and-roll.

Owens is revisiting the imperious manner that Metropolitan Opera-goers saw in the John Adams Doctor Atomic, in which he played a military general who struggled with his diet. "All I need is the Hershey bars," he cracked at rehearsal Friday, referring to what his Doctor Atomic character munched when not singing.

The project is a breakout for Dolce Suono Ensemble, a group that began as a small-scale series of chamber music concerts in 2005. It quickly outgrew its University of Pennsylvania venues and will be performing at the more mainstream Trinity Center of Urban Life on Wednesday. Though Dolce Suono has always had some of the best Philadelphia Orchestra musicians - not to mention its founder, virtuoso flutist Mimi Stillman - landing Owens and A-list composers such as Mackey raises the group's profile in Philadelphia.

The big question is, how did Stillman do this?

"Blood, toil, tears, and sweat," she said. "Sometimes I think that running a big project like this is like running a small country."

The 29-year-old flutist, who plays a broad range of new and standard concerto repertoire with orchestras around the country, also wrote her own grant proposals. The result has been money from the the Philadelphia Music Project, the Aaron Copland Fund for New Music, and the National Endowment for the Arts, which allowed her to commission - in addition to Mackey - Steven Stucky, David Ludwig, Fang Man, and Stratis Minakakis.

Writing for Owens was certainly an artistic incentive. Ludwig scoured the Internet for Owens performances and concluded, "There's nothing he can't do."

Owens himself was persuaded to come aboard early. He and Stillman crossed paths when both were students at the Curtis Institute of Music (which she entered at age 12), and she approached him two years ago. Though currently entrenched in the Metropolitan Opera's Ring cycle - his portrayal of Alberich has won superlative reviews - he tends to jump at the chance to do smaller-scale recitals, which are more difficult than opera but also more satisfying.

Also during Wednesday's concert, he'll revisit Mahler's Songs of a Wayfarer in the Schoenberg chamber orchestration - a paragon of depressive 19th-century romanticism in which even the cheerful moments are tinged with the melancholy of romantic disappointment.

"It can be cathartic in a way," says Owens. "You can channel all of your baggage into these songs cycles ... especially if something is going on in your life that's mirroring the songs. ... People say, 'Wow, you were really living those songs.' And I say, 'Yeah, I was.' "

He also has a taste for new music, having premiered Adams' 2006 A Flowering Tree (as well as 2005's Doctor Atomic) and starred in Ligeti's Le Grand Macabre last year with the New York Philharmonic. In addition to Mahler, Owens sings four of the five new pieces, including Song of Sorrow by Fang Man, which has a Chinese text. The language is new to Owens.

"I'll hammer away at it for hours and then I go back and it's like looking at it for the very first time," Owens said. "What was I smokin' when I agreed to do this?"

The idea of the piece was to return the texts Mahler used in his Das Lied von der Erde to their original Chinese. Other composers set poems by poets Mahler loved, or, in the case of David Ludwig, the folk poem Ewigkeit from the Des Knaben Wunderhorn collection "that Mahler might as well have set to music," says the composer. "It's titled 'Eternity.' Very Mahlerian. I wrote a slow march ... the slow march of time is what I was going for."

A two-year endeavor, the February 2012 installment of Mahler 100/Schoenberg 60 Project will feature Schoenberg's revolutionary Pierrot Lunaire and a major new work by Shulamit Ran. The Philadelphia performances will be followed by a spot in the Composers Now series at New York's Symphony Space.

The project is characteristic of Stillman, a musician with a wide range of interests - musical and not - but an instrument whose repertoire is relatively small and not always representive of any given composer's greatest moments. That's changing with new flute concertos by Kaija Saariaho and others, and Stillman has done her part to help things along by premiering new works by David Finko and playing new-ish works by Lowell Liebermann and David Amram.

Her passion for Mahler fueled the current project, and Schoenberg was a natural juxtaposition: Both shared a Jewish/Viennese sensibility, and Schoenberg's chamber reductions of Mahler works put them in reach of Dolce Suono Ensemble, a loose collective that consists of two to a dozen musicians at any given concert.

"I've always felt free to pursue my own artistic path, to learn and explore and formulate who I am," said Stillman. "My teachers, Julius Baker and Jeffrey Khaner, always fostered that ... and that's why I started Dolce Suono. It's taken me places I never imagined."