Tip: See my list of the 
MostIf you are wondering whether you should say that something sounds “good to your ear” or “good to your ears”, rest assured that either choice is fine (and, of course, the adjective does not have to be “good”). Nevertheless, if you want to be on the safe side, use the plural, which seems to be more common, e.g.
The sentence sounds good to my ears.
There are, however, a few idioms where the plural is not optional. The phrase “being in something up to one’s ears” means “being very busy or overwhelmed with something”, for example,
I am up to my ears in work. (correct)
I am up to my ear in work. (unnatural)
When you say that something is music to your ears, it means that it is exactly the thing you wanted to hear, e.g.
His apology was music to my ears. (correct)
His apology was music to my ear. (unnatural)
It can also mean that it is very pleasant or soothing, as in
Your voice is music to my ears.
