Fresh Pieces, Crisp Players - NYTimes.com Tina FIneberg for The New York TImes Rebekah Heller will perform with the International Contemporary Ensemble and on her own. Among the many changes that the Mostly Mozart Festival has instituted in recent years to shore up intrigue and innovation, few have stood out as sharply as this season's residency by the International Contemporary Ensemble. A reliably persuasive new-music group, the ensemble opens the week with fresh pieces by Felipe Lara and Tyshawn Sorey on Sunday, and by Maria Stankova and Nathan Davis on Monday. On Tuesday, the ensemble celebrates the 80th birthday of the maverick composer Pauline Oliveros, collaborating with her in a range of chamber works. A final offering on Thursday pairs a premiere by George Lewis with Beethoven's Septet in E flat. Tickets are scarce for most of these events, but there's one more option: on Saturday at Spectrum, a downtown loft space, the ensemble's bassoonist Rebekah Heller celebrates the release of "100 Names," a pensive and potent solo CD. Sunday, 7:30 p.m. Monday, Tuesday and Thursday. Clark Studio Theater, 165 West 65th Street, Lincoln Center; 212-721-6500, mostlymozart.org. 7:30 p.m., Saturday, Spectrum, 121 Ludlow Street, Lower East Side; 650-400-5100, spectrumnyc.org.)