Here is the song at the very top of my most-played list. Take it as a mother-son song, as the mother being: 1) Ajay Rathod's mother (in the film); or 2) the country of India (I thought both were relevant in this case, the latter being more obvious). Either way, it is a fantastic song, and easily one of the best Lata songs of the decade in my humble opinion. The last minute of the song is truly one of the best pieces we could hope to listen to in a duet.
From the movie Rang De Basanti (2006), with vocals by Lata Mangeshkar and A. R. Rahman, music by A. R. Rahman, and lyrics by Prasoon Joshi (who also wrote the songs for Taare Zameen Par and the song Maa).
Here is an interesting video of the making of the song at A. R. Rahman's studio:
And here is the song as it appeared in the film: