Is Van Morrison the world-weary rock ‘n’ roll warrior of “Don’t Go to Nightclubs Anymore” and “School of Hard Knocks,” the existential philosopher of “No Thing,” or the spiritual sentimentalist of “Behind the Ritual”? Remarkably, he’s all of these at once—and more. Drawing on decades of musical mastery and the many roles he’s inhabited, he brings a weapons-grade level of gravitas to all of the above on Keep It Simple. And he does it with a deft blend of blues, R&B, country, and gospel influences, shot through with some slow-burning charisma.