I don’t have an ear for music.
Some of you may find this Japanese sentence strange, but it’s actually a very natural way of expression in Japanese. Another example in the same pattern of 分からない is:
私にはワインの味が分からない。= (lit.) I don’t understand the taste of wine. = I cannot distinguish different types of wine by tongue. = I have no taste buds for wine tasting.
I personally prefer inserting に between 私 and は, though.
私には音楽が分からない。= The average people probably do, but I don’t have an ear for music.
私は音楽が分からない。= I am the one who don’t have an ear for music. (And I don’t know/care whether the average people do or not.)