Lynn Poole displays a chart of the orchestra sections: strings, woodwinds, brass, and percussion. Dr. William Hart, timpanist with the Baltimore Symphonic Orchestra and professor at the Peabody conservatory of Music, defines the elements of music: rhythm, melody, and harmony and demonstrates each of them on the piano, noting that the percussion instruments are the dispensers of rhythm. He gives a brief history of percussive music while showing instruments such as the timbro, castanets, cymbals, tambourine, and Chinese temple blocks. With the assistance of fellow timpanist Dr. William G. DeLeon, Dr. Hart demonstrates and explains the snare drum, the most common percussive instrument; the xylophone and its use in modern compositions such as the "Sabre Dance"; the cymbals and their contrasting use in Wagner's "Die Walkure" and Debussy's "Festivals"; and the kettle drums, or timpani, which can be tuned and which provide the heartbeat of the orchestra.