The raga is a form of Indian classical music that is written to be performed during a particular time of day: morning, noon, or night. This weekend, ragas will permeate the air in Central Park, as part of the fourth annual "Ragas Live" festival, a two-day event designed to celebrate the summer solstice (the longest day of the year) as well as Indian music. Closing Sunday night is the acclaimed American clarinetist Shankar Tucker, who has made a life's work of studying and promoting Indian classical music.