By far the most dynamic and popular music of Pakistan is qawwali, which has been internationally popularized by stars like Nusrat Ali Khan. Qawwali, in multiple forms, is widespread throughout Pakistan and Northern India. Qawwali refers to both the performance and the genre of music. Qawwals typically consist of a lead vocalist, two back-up vocalists and any number of percussionists. Qawwalis are traditionally led by a sheikh and are meant to help the audience realize the mystical ideals of Sufi Islam. Amir Khusrau is said to have invented qawwali in the 13th century; the legendary poet and composer is also said to have invented the tabla and sitar. The idea of music (sama) inspiring an understanding and love for the divine and communication with spiritual guides is known from at least the 9th century. Orthodox Muslims sometimes criticize qawwali for its erotic imagery and sometimes frank sensuality. Qawwali is similar to Hindustani musical genres; it has three components: a rhythm (traditionally played on the dholak), the melodic line of the vocals, and the pitch of the melody which is reinforced on harmonium. Poetic verses are usually mixed with a chorus and instrumental passages. Traditional languages used include Persian and an ancient form of Hindi called braj bhasha, as well as Punjabi, Urdu and Arabic. The ancient tradition of tarana, a rhythmic series of nonsensical syllables with meaning only to the singers, if anyone, has helped lead a fusion with qawwali and jazz, due to the parallel practice of scat singing. Qawwali fusion with filmi and Western pop music have achieved some popularity, with attendant criticism from purists for allegedly watering down the sacred sound of qawwali. Nusrat Fateh Ali Khan, Sabri Brothers and Rizwan-Muazzam Qawwali Group have become especially popular, especially after Nusrat's collaborations with Michael Brook (a Canadian producer), resulting in the unexpected hit of "Mustt Mustt", remixed by Massive Attack and popularized by its use in a Coca-Cola television commercial.