According to the journal Alternative Therapeutics in Health and Medicine, "designer music" -- a recording that promises to make you calmer, or smarter, or maybe just improve your digestion -- can usually do what it claims.
Researchers asked 144 subjects to listen to 15-minute selections of grunge rock, classical, new age and designer music. After 15 minutes of grunge rock, the listeners showed more hostility, sadness, tension, and fatigue, and reductions in caring, relaxation, mental clarity and vigor. The classical and new age selections had mixed results in terms of altering emotions.
But the designer music, which was intended to increase positive feelings and reduce negative feelings, actually accomplished what it set out to do.