‘Two Different Moods’ in a single song

I was listening to the songs of 'Sharmili' the other day. One song struck me as interesting, 'Megha Chhaye Aadhi Raat'. Even if the song is not a happy one, the prelude and the interlude of first stanza (Antara), have a completely different mood. The other part of the song has a gloomy mood. Sharmili …