Bollywood music forms the soundtrack to Bollywood films. The term 'Bollywood' is often incorrectly used to refer to the whole of Indian cinema; it is only a part of the total Indian film industry, which includes other production centers producing films in regional languages. Nevertheless, Bollywood, based in Mumbai, Maharashtra, is the largest film producer in India and one of the largest centers of film production in the world.
The language of Bollywood songs can be complex. Some are saturated with Urdu and Persian terms and it is not uncommon to hear use of English words in songs from modern Hindi movies. Several other Indian languages have also been used including Braj, Bhojpuri, Punjabi and Rajasthani. Occasionally a few lines in other Indian languages are used as well.