The newly announced Philadelphia Orchestra's 2017-18 season will include a concert version of Tosca starring soprano-on-the-verge Sonya Yoncheva, a semi-staged West Side Story to toast Leonard Bernstein's 100th birthday, and a chamber-music appearance by none other than Yannick Nézet-Séguin on piano.

After a season that often took refuge in the safest of classical hits, next year's appears to consolidate the Philadelphians' circle of regularly visiting artists while allowing them to go to far more adventurous places. Newly written concertos -- previously concentrated in a series of festival-style concerts -- are now sprinkled throughout the season.

Nézet-Séguin says some of the large-scale programs in his sixth season as music director -- including the infrequently heard Haydn oratorio The Seasons (Nov. 16-18) and the Tosca with Yoncheva (May 12, 16, and 19, 2018) -- were years in the making. He first sang Haydn as a boy chorister in his native Montreal. As a mature conductor there, he has conducted Tosca -- but only Act I.

"I finally got the Tosca that I've been dreaming about," he said. "It's a Puccini opera that I have not so far conducted complete. ... This will be a role debut for Sonya, and something we've been talking about even before Otello [her Metropolitan Opera breakthrough, conducted by him, in 2015]."

Of course, his becoming music director-designate at the Met starting later this year can't help being an attraction to A-list singers. But Nézet-Séguin has always had a special relationship with singers.

In the coming years, with both the Met and the Philadelphia Orchestra under his leadership, Nézet-Séguin envisions an exchange of talent in various forms. "I would like to see something more creative than just conducting something at the Met and taking it down to Philly to do it in concert," he said in a phone interview from Montreal. "But I'm not saying that will never happen."

Another longtime dream will have Nézet-Séguin as a chamber-music pianist: Three weeks of  Winter Festival: British Isles concerts in January 2018 will begin with Elgar's infrequently heard Piano Quintet, heard not as a prelude or postlude concert, but in the opening subscription concert -- partly because, as he says, the quintet is orchestral in scope.

His periodic installments of Bruckner will continue with the grandest piece of them all: Symphony No. 8 (Nov. 9-11). Nézet-Séguin has long felt this is the one composer he may have conducted in a previous life: "When I first did the Ninth, I did it from memory right away and I remember telling my parents: I feel like I've been doing this before."

The Deutsche Grammophon-label Rachmaninoff concerto recordings with Daniil Trifonov will continue, not in private studio sessions as before, but with Concertos Nos. 2 and 3 each performed twice over four concerts, April 12-15.  Ongoing conversations with the Dutch violinist Janine Jansen resulted in her March 8-10, 2018, concerts featuring a work written for her by Michel van der Aa, who is well-known in Europe but not in the U.S.

Elsewhere in the season, Hilary Hahn will return, not for just another concerto appearance (though she'll play Prokofiev's Violin Concerto No. 1 and Bernstein's Serenade), but as artist in residence. The range of her other activities is not fully formed but is likely to include the kind of outreach work she pursued as a Curtis Institute student to communities beyond Center City. She's also working with the principal guest conductor Stephane Deneve (who leads four subscription weeks) on a new version of Peter and the Wolf.

Composers will also be delving into the fabric of Philadelphia. Tod Machover has been creating a series of "crowd-sourced" pieces that are meant to capture the flavor of a particular city, and will be doing so with the premiere of Philadelphia Voices in partnership with various choirs, conducted by Nézet-Séguin, on April 5-7, 2018. Composer in residence Hannibal Lokumbe will be in similar dialogue with different parts of the community, such as the Philadelphia Detention Center, for the creation of Healing Tones that will be heard in the 2018-19 season.

Among the six new and near-new concertos are two of Jennifer Higdon's more unorthodox works featuring multiple soloists (as opposed to just one). On a Wire will showcase the new-music ensemble eighth blackbird Oct. 19-21, and in a new co-commission by the orchestra, Concerto for Lower Brass will showcase the brass section Feb. 22-24, 2018. Another orchestra commission will be a flute concerto for principal Jeffrey Khaner by Samuel Jones on Jan. 5 and 6, 2018. Violinist Nicola Benedetti plays Wynton Marsalis' Violin Concerto on Nov. 2-4.

For the Bernstein 100th birthday program Oct. 12-15, Nézet-Séguin was inspired to conduct the semi-staged performance of West Side Story partly because of its distinct differences from the film, which the Philadelphia Orchestra has played in concert in past seasons.

Notable guest conductors include Fabio Luisi (Jan. 24-26), Christoph Eschenbach (Feb. 1-3), Michael Tilson Thomas (March 1-3, 2018), Nicholas McGegan (May 4-5, 2018), and two notable newcomers: the hot Lithuanian conductor Mirga Grazinyte-Tyla (Feb. 8-10, 2018) and Lahav Shani (March 22-24, 2018). The former was named Andris Nelson's successor with the City of Birmingham Symphony Orchestra and the latter is the next chief conductor of the Rotterdam Philharmonic Orchestra -- though Nézet-Séguin, whom he succeeds, says he had planned to bring Shani to Philadelphia before the appointment was made. Star soloists include Joshua Bell (Feb. 15-18, 2018) and Helene Grimaud (May 10-20, 2018).