Sebastian Chang's first major performance as a piano soloist was of his composition Concertino for Piano and Orchestra with the Tokyo Symphony at the age of 9. Sebastian obtained his B.M. in Composition from the Curtis Institute of Music and an M.M. in Composition from the University of Southern California. From 2016 to 2018, Sebastian was the resident composer for the Louisville Orchestra.

Sebastian is the youngest three-time recipient of the BMI Student Composer Awards. He received his first award at the age of 14 (receiving the Carlos Surinach Prize that year for being the youngest recipient), his second award at the age of 17,, and third award at the age of 19. BMI has reduced the maximum amount of awards per individual from three to two.

Sebastian's compositions have been performed by the Detroit Symphony Orchestra, the Philadelphia Orchestra, the Tokyo Symphony Orchestra, the Pacific Symphony, the Britt Festival Orchestra, the Louisville Chamber Choir, the NouLou Chamber Players, the Louisville Ballet, and the Louisville Orchestra.

His First Symphony, premiered in January 2015 by the Louisville Orchestra, is the subject of Episode 9 of PBS's Music Makes a City documentary series.

"Between Heaven and Earth," based on oil paintings of visual artist Vian Sora, premiered on February 2018, performed by the Louisville Orchestra and Louisville Chamber Choir at the Kentucky Center in Louisville, Kentucky.

"Cryptogenic Infrastructure Fantasy" (C.I.F.), for violin, clarinet, piano, and timpani, received its premiere in July 2018 at the ChamberFest Cleveland by Diana Cohen on violin, Franklin Cohen on clarinet, Alexander Cohen on timpani, and Roman Rabinovich on piano. Performed at the Maltz Performing Arts Center in Cleveland, Ohio, C.I.F. received its second performance at St. Stephen's Anglican Church in Calgary, Canada, in December 2018.

Sebastian's new Piano Concerto, "The Empress," for piano and full orchestra,  premiered on June 17, 2022, in Jacksonville, Oregon, by the Britt Festival Orchestra, conducted by Teddy Abrams.

He is Louisville Orchestra’s first-call pianist. He worked the summer 2022 Britt Orchestra Season as Orchestral Pianist following the premiere of his Piano Concerto. He is an instructor in the piano conservatory at the Orange County School of the Arts.

Sebastian freelances around Orange County and Los Angeles as a keyboardist. His publishing company is Sebastian Press, registered under the American Society of Composers, Authors & Publishers (ASCAP).

Sebastian is a Davidson Fellow Laureate through the Davidson Institute for Talent Development.