Deleting Music/Voice Memo from "on my device" library in Itune

Hi, May I know why does apple make it so difficult to remove music or voice memo from the iTunes library? I added some voice memo/music which was needed for work then, and do not need them now.

I have spend hours, looking through the web/youtube to find a way to delete them from my library and yet to find any solution.

So,

1) Please provide me with a solution on how I can resolve this issue

2) Going forward, please add the delete function/button so that we can just remove them easily.

Thank a million