Having a tin ear is colloquially used to refer to someone's inability to discern sounds, particularly in music. There are several synonyms and idiomatic expressions that can be used in place of "have a tin ear." Some of these include having a deaf ear, lacking musical sense, being tone-deaf, or being musically challenged. All these terms describe a similar condition where an individual struggles to appreciate the nuances or complexities of music. However, it's essential to note that not having an ear for music does not necessarily translate to a lack of other skills or talents, and should not be used to ridicule or belittle an individual's outlook towards music.