An instrumental hip-hop beat crafted from a snatch of “Triadic Memories” by the late composer Morton Feldman, who is beloved for his extended and extravagantly silent music? Why yes, thank you. This is “Memory” by Bstep. It’s barely a minute in length and takes a single, five-note segment — a splinter, really — of Feldman’s celebrated solo piano work, and then lays it above a spare metric pulse. The added beat is so spare, so old-school, it might have been something that Feldman, who died in 1987, heard during a visit to Manhattan for a concert premiere in his later years. What makes “Memory” work is how it teases out of that final note of the five-note figure a thin wisp of sound that then lingers over the beat like a fog.