Thanks for the responses, friends :)
Anniyan, 'idhayam idhayam' is a wonderful song indeed! I love the place where its desecends so gracefully in 'poo meni anjumo, mayil iragail manjamo'. We must have it in SOTD sometime.
Chandrabose's voice was well suited for the 'rasa vandhaadi' song. He sings the washerman's lines 'paavangalai manushan ellaam gangaiyile kazhuvuraan, andha padu paavi manushan azhukkai inge vandhu thuvaikkarirom' (Lyrics: pulavar Chidambaranathan). Btw, Shyam was a good singer too- have you heard him sing 'kaathu adichidhu' in kuppathu ponnu?
Mouli and Jayadevi gave Shyam some great opportunities. It was Shyam's bad luck, as Raj Chandra says, that most of the films for which he composed music were commercial failures.
Some other forgotten gems of Shyam worth rediscovering : 'pura rendu vaanil sendru' (kuppathu ponnu/ SPB & SJ), 'vaa vaa aadi vaa' ( Jaathi pookkal/ JC), 'poo maalaigal' (jaathi pookkal / JC & SJ), 'andhi malli' (naan nandri solven/ SPB & PS), 'megangale' (sandhosha kanavugal/ SPB & PS), 'maandhalire' (devathai/ SJ), 'sollathaan ninaithen'- SPB & 'unnaithaan azhaithen'- KJY (both in the same tune, from vilangu), 'mai vecha kannamma' (Sridevi/ SPB & PS), 'iravum pagalum' (nee sirithaal naan sirippen/ VJ), 'vedhanai kaattil' (unarchigal/ PS & SJ)