app_engine,
I haven't heard the thangamagan song (Dont be surprised. I haven't heard a lot of songs) but the feel of 'Chandamama Raave' is very similar to 'Kalaya Nijama', though both are very distinct songs. 'Mallepoovu' is an excellent album and I have been listening to it almost on a daily basis.
Some people have claimed that 'Hero Nenochane' sounds old. I feel that in this particular song, IR has used Mohanam in such a way that it has a vintage feel. My thinking is that IR has deliberately given this feel for the song. I like this song.
S.Suresh