Editors' Notes In the late ‘50s, "mood music" soothed anxious listeners with popular melodies set to sedate string arrangements. Today's easy listening, a.k.a. "adult contemporary," is like plush and cozy musical pajamas that never go out of fashion. These essential tracks don't have a specific style or era in common so much as they share a crucial trait: familiarity. Easy listening's high-profile songs are instantly identifiable classics by blue-chip old (and young) masters like The Beatles, Norah Jones, and Ed Sheeran. Mellow folkies like James Taylor and Simon & Garfunkel, as well as big-throated crooners like Barbra Streisand and Diana Ross, may have put the crucial "ease" in easy listening, but the style isn't only about pop's soft side. Whitney Houston and Céline Dion raise the energy level with passionate, soaring vocals, while chart-topping pop-rockers like Train, Los Lonely Boys, and John Mayer bring guitars and gruffness to the quiet riot.