From link in http://www.tamilnation.org/culture/drama/index.htm (check also http://eprints.soas.ac.uk/3596/1/MusicIntheAgeofMechanicalReproduction.pdf) about the article "Music in the age of mechanical reproduction: Drama, gramophone and the beginnings of Tamil cinema" by Stephen Putnam Hughes":
"This paper takes on the issues of why and how film songs became such an important and persistent feature of Tamil cinema. The specific focus is on how the relationship between Tamil musical drama and the south Indian gramophone business preceded, mediated and was, eventually, transformed by the emergence of Tamil cinema as a dominant commercial entertainment during the 1930s. This is, in part, an attempt to reconsider conventional explanations for why the first Indian talkies featured songs as the main, if not defining appeal of their entertainment. "
The paper does not seem to be freely accessible now. I have downloaded a copy when it was free and it is an interesting article.