Answer:
Major or minor I can be, when you touch me make sure you that you’re on the right key.
It's shorter than the rest, but when you're happy, you raise it up like it's the best. What is it?
The more you have of me, the less you see. Who am I?
The buyer doesn’t want it, the producer doesn’t need it and the user doesn’t know their using it.
Split me in half, and you get me and another me. What word am I?
Two little holes in the side of a hill. Just as you come to the cherry-red mill.