Pianist Dejan Lazic, dressed completely in black, bent his slim frame toward the piano Thursday night, splaying out his fingers on the keyboard, and hammered away. During this a cappella break in his 2014 composition, "Concerto in Istrian Style," performed with the Atlanta Symphony Orchestra at Symphony Hall, Lazic summed up every bit of music in the piece — thorny, disjunct spindles of notes, dense chords played with a biting intensity, sweet, soft melodies.

Without accompaniment by the ASO, Lazic’s approach became a compelling, curious window into the mind of the Croatian pianist/composer. When the orchestra joined in, either mirroring Lazic’s pianistic ideas or providing a musical springboard for the pianist, the performance occasionally lacked cohesion. Serene passages — among them a gauzy, all-encompassing cloud of gorgeous strings — often emerged, but sometimes Lazic’s sparse arrangement led to orchestral challenges.

It’s fitting that Spano brought the pianist back to Atlanta for a concert that promised music “on the cutting edge of classical.” Last year, Sony released a world premiere recording of the ASO and Lazic interpreting a reimagined Brahms concerto, and the pianist’s involvement with Spano goes back even further. The pianist is the perfect candidate to challenge the orchestra.

Spano's dedication to new music and 20th-century compositions may be one of the ASO's greatest assets. Music directors that program a predominance of older music are allowing audiences to forget that today's classical music is a living, breathing art form. Composers writing today may premiere a piece of music only to return to tinker, expand and continue to make adjustments. When ASO bassist Michael Kurth helped perform his "A Thousand Words" during opening night last month, the piece had seen revisions since its world premiere during the 2015-2016 season.

For Michael Gandolfi, a member of the Atlanta School of Composers, this tinkering involves adding movements and ideas to an ever-expanding musical tribute to the Garden of Cosmic Speculation, a 30-acre green space in Scotland. “A Garden Feeds Also the Soul” comprises two new movements of the work, which Gandolfi and the ASO recorded, in 16 parts, in 2007. Beginning with recorded bird sounds, the impressionistic recording cycles through Gandolfi’s many musical impressions of the garden.

After adding onto the work last year with two movements premiered by the Grant Park Orchestra in Chicago, Gandolfi brought two more additions to the ASO. “The Bone Garden” is a highly programmatic work that, at the start, depicts leaves rustling on the ground, wind howling through the trees and bones clanking and clanging together — perfect for the opening scene for a slightly scary Halloween movie. A simple melody sits atop a murky and ominous chaconne figure in the low strings, giving the movement the feeling of a macabre dance. “The Scottish Worthies” oozes picturesque pastoral imagery — complete with fluttery piano and nimble bass pizzicato — for a totally different outlook of life from its musical partner.

After intermission, the ASO returned from a first half of new music to a trusted classical master. During Sergei Rachmaninoff’s Symphony No. 3, the ensemble played with vigor and passion, capping a night of new music with the sound of the familiar.

CONCERT REVIEW

Atlanta Symphony Orchestra

8 p.m. Oct. 12. Additional performance at 8 p.m. Oct. 14. $32-$97. Symphony Hall, 1280 Peachtree St. NE, Atlanta. 404-733-5000, www.atlantasymphony.org.

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T-Boz talks about group mate Lisa Lopes in Atlanta Oct. 9, 2017, during an event at Rich Auditorium to promote her book, "A Sick Life."