Did sentence has some mistakes yet?

This sentence is wrong in grammar.
I didn't know what was (we use “was” but not “are” because all you are talking about happened in the past) good music and voice until I heard her songs
In fact you should also change to : what good music and voice was, not what was good music and voice because this is not a direct question.
Therefore the final version is :
I didn’t know what good music and voice was until I heard her songs.

ok