Reich, whom the New Yorker called “the most original musical thinker of our time,” celebrates his 80th birthday in 2016; the year also marks the 40th anniversary of the premiere of Music for 18 Musicians, considered by many to be his greatest composition. Two of Chicago’s world-class ensembles, Eighth Blackbird and Third Coast Percussion, team up to perform this seminal piece. Reich’s Sextet rounds out the program.