In a bad mood? Grab your MP3 player. Bach or Beck? Doesn't matter. Music of almost any kind will lift your spirits, say researchers Annette Kalanowski and Valerie Stratton of Penn State's Altoona campus. The two asked 47 students—music and non-music majors—to track their tunes for two weeks. Rock stole the show, followed by classical for music majors and country for the non-majors. The audiophiles averaged a couple hours of music each day—while studying, driving, eating, and getting ready for class in the morning. All that listening worked wonders, decreasing negative moods—like sad, hateful, aggressive—and increasing positive moods—like joyful, optimistic, and friendly. Turn it up!