Mingus Ah Um just might be the most welcoming point of entry to the sprawling continent of jazz. Fierce in expression but controlled in form, the 1959 LP draws out a rootsy warmth from beneath the bebop that had consumed bandstands since World War II, forging a sound that feels at once confrontational, mischievous, and generous. Charles Mingus—bassist, composer, irascible iconoclast—had a large, rotating ensemble, a collective called the Jazz Workshop that he treated like one of the anti-mainstream theatrical troupes that had cropped up all over his home of New York City. Mingus and his faithful were about both...