An important ancient Hindu musical form known as the Dhrupad has been very important in the history of Indian classical music. This style is supposedly free of Islamic influence and is considered an unadulterated pure form of raga, and is a significant inspiration for more modern classical music. Dhrupad, one of the most difficult of all styles in Indian classical music, presents the raga in its most pure form, without the typically elaborate ornamentation and embellishment practiced in most other styles. Dhrupad is considered the most difficult type of Indian classical music to sing, and performances today are rare. A dhrupad performance requires supreme strength and vocal control, and may last several hours. The dhrupad is often associated with the pomp and grandeur of the Mogul courts and with the "most correct" way to sing a raga. In the dhrupad the lyrical text must be clear; it is composed in four brief sections, though improvisation occurs. The dhrupad is largely rhythmic in orientation, featuring manipulations in double and quadruple speed and manipulations of the text. It is of primary concern to enunciate the text clearly and to keep strictly to the rules of the raga.