Last night Seattle-based rapper Sir Mix-A-Lot joined contemporary composer Gabriel Prokofiev on stage at Benaroya Hall to rap along to an orchestral version of “Baby Got Back.” Prokofiev, grandson of Russian composer Sergei Prokofiev, is the pioneer of a genre he calls “nonclassical,” or the blending of electronic and classical composition. In an illuminating interview with The Quietus earlier this year, he shed some light on the whole thing: “There are certain ways of listening and certain aesthetic values that can be different, I know that there is some music I’ve made that won’t work in a concert hall setting, and vice versa, but there are some magical moments when the two worlds collide successfully.” This seems to be one of those successful collisions, at least if we go by how many audience members were dancing on stage. Watch video of “Baby Got Back” and “Posse On Broadway” below.