He is an expert in musicology and has a deep knowledge of classical music.

I like listening to light music.

I like listening to classical music.

There is a wonderful band in my town.

It's better for him not to know the truth. After all, ignorance is bliss.

He knows that pain through his own experience.

He is feigning ignorance about that problem.

In order to understand his feelings, I had a deep conversation with him.

God only knows what he is thinking.

I have no way of knowing what he is thinking.