In order to be amoral, music must be inherently neither good (righteous) nor bad (the absence or opposite of good).
Clearly the use of music is far from amoral, it can be used to praise God, and it can be used to mock, criticize, and drive people from Him. So, music can certainly be used for good or for bad.
I believe that you cannot separate something from it's use, especially an activity. Wielding a weapon can be used for good and for bad, and thus, I believe, is not amoral. Writing, speaking, art, theater, all these can be good or bad, they are not only used for good or ill, they are themselves good or bad.
Proverbs 8:13 says:
To fear the LORD is to hate evil;
I hate pride and arrogance,
evil behavior and perverse speech.
How can speech be perverse if it is not bad? How can behavior be amoral if it is evil?
We are actually commanded to make music, to sing praises to the Lord. A few scriptures that show this:
Rejoice in the LORD and be glad, you righteous; sing, all you who are upright in heart! -Psalm 32:11
Speak to one another with psalms, hymns and spiritual songs. Sing and make music in your heart to the Lord - Ephesians 5:19
Thus, music can be good. I don't mean good as in “nice,” but good as in fulfilling God's perfect will. How can something that we are commanded to do be neutral? Music that builds up, brings praise to God, and edifies the saints is good; it not just used for good, but it is good.
However, anything in this fallen world that can be good, can also be bad. Speech that is full of sinful messages is not only being used for evil, it is itself bad. Speech can be good or it can be bad, songs are the same way. Music that is full of profanity, drugs, and sin is not just being used for evil, it is itself bad.
Basically, you cannot separate an activity from its purpose. An activity with an evil end is itself bad. An activity with an end that glorifies God is itself good. Therefore, music is itself either good or bad, and is not amoral.