Documentary a sentimental look at Mr. Rogers

In the intimate opening of the riveting Won’t You Be My Neighbor?, Fred Rogers (circa 1967) is ruminating about musical modulation: Moving from the key of C to F is easy, but going from F to F sharp is more complicated, he says. That strikes a chord, in his mind as well as his piano: “We’d like to help children through some of the difficult modulations of life.”