Christmas music is a nostalgia trip. Poly Styrene, “Black Christmas” “I’m dreaming of a black black Christmas/Black smoke glows against a midnight sky…A child is born on Christmas Day/But they crucified him anyway.” The bleakest Christmas song ever written? Los Lobos, “Llegó Navidad” In 2019, East L.A.’s — or, maybe, America’s — finest rock ‘n’ roll band released “Llegó Navidad”, …