He was 88 and is survived by four sons and three daughters.
"The cremation will be held tomorrow, he passed away after about a month's medical treatment for old age related illness," Viswanathan's son Gopi told PTI.
Affectionately called by the acronym "MSV," Viswanathan was a household name in Tamil Nadu, his death was condoled by the Tamil film fraternity and political leaders.
Expressing grief, Chief Minister Jayalalithaa said he remained a legend in Tamil cinema.
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Together they shared the famous creditline of "Viswanathan-Ramamurthy."
His association with iconic lyricist of yesteryear "Kaviyarasu" Kannadasan is legendary and it resulted in evergreen songs and he came to be called as "Mellisai Mannar" or King of Melody.
Anecdotes of how MSV used to compose music with his humble harmonium to Kannadasan's lyrics are popular in Tamil Nadu.
MSV also acted in character roles in over 10 films, including Tamil comic hit "Kadala Kadala".
"Pasamalar," "Paavamannippu," "Paalum Pazhamum," "Par Magaley Par," "Padithhal Mattum Podhuma," "Deivathaai," "Panam Padaithavan," "Padagotti," "Anbe Va," "Parakkum Pavai," "Ramu" and "Thamarai Nenjam" were among the super hit Tamil films, the songs of which still reverberate in every nook and cranny of Tamil Nadu.
His Telugu hits include "Maro Charithra" (made into Hindi as 'Ek Duje Ke Liye), "47 Rojulu," "Tenali Ramakrishna," "Maa Gopi," "Ramu," "Kokilamma," "Laila" and "Samrat Asoka".
"He brought about several changes in music composition and successfully integrated elements and traditions of folk, rock, jazz, carnatic, western and western classical in film music," film music researcher D Thiagarajan said.
"Sonnathu Needhana" (Nenjil Oru Alayam), "Viswanathan Velai Vendum" (Kadalikka Neram Illai), "Kettavarellam Padalam" (Thangai) are among MSV's all time favourites that are still popular in Tamil Nadu.