Question

what is the meaning of ring a bell? you may have mentioned this book before, but the title doesnt ring a bell. to play an instrument to sound familiar to be very expensive

Explanation:

The phrase "ring a bell" is an idiom. In the given sentence "You may have mentioned this book before, but the title doesn't ring a bell", it implies that the speaker has no recollection or familiarity with the book title. "To play an instrument" is a literal interpretation which doesn't fit the context. "To be very expensive" is also not relevant. The idiomatic meaning is about familiarity.

Answer:

to sound familiar