Straight From Heart:

In my experience , I have apparently felt that the best music and poems have been the ones which convolutes and congregates a spectrum emotions and feelings both implicit and explicit in so few words or with a few notes of music that a listener cannot help but be mesmerised.

Of the spectrum, the strongest of feelings would come as pain , sorrow , loss of one dearest to heart, failure not necessarily in the order.

The people who are writer and poet stuff have strong abilities to feel things.

I say, the lyrics are the very strength here:

Just heard this lovely song by Kailash Kher:

I really loved the way the phrase "Tu kya Jaane" has been very beautifully delivered by Kailash Kher.

The line that goes on repeating is this song  has meaning as:

The fact that you are you are ruthless and heartless is even known to god. ( Hence I need not to prove this to anyone in this world ).
As such you can never know what's the pain that ails my heart...