I understand with this quote that the song should not be a forced one in a film, rather the audience should not know when the song started. The song should also carry the story with it. I believe it is not just without lip sync. There are hundreds of songs without lip sync. Even there can be song with lip sync and still they can be close to real. If I am right, few songs mentioned here may not satisfy the thread criteria, especially those MGR songs and even salangai oli or Indian songs or even the Subramaniapuram songs and that takes the beauty out of this concept and thread. Please correct me if I am wrong.
+1, all those "dream songs" "foreign songs" etc may not belong here, IMHO (thread originator, venkkiram, to correct if not so)