Complex sentence: The rubab holds as the first instrument used by Sikhism, it was used by Bhai Mardana the companion of Guru Nanak whenever a shabad was revealed to Guru Nanak he would sing it and Bhai Mardana would play it on his rubab he was known as a rubabi.
Split into simpler sentences: The rubab holds as the first instrument used by Sikhism; it was used by Bhai Mardana the companion of Guru Nanak. Whenever a shabad was revealed to Guru Nanak he would sing it and Bhai Mardana would play it on his rubab; he was known as a rubabi.