In iOS 7 and earlier, if you wanted to delete music from your iPad, you had to do it on a song by song basis in the music app. In Settings>General>Usage>Music you only had the option to delete all of your music at one time. There was no option to delete music on an album basis. That's all changed with iOS 8. When iOS 8 is released this fall, you'll be able to go into settings and selectively delete artists, albums, and individual songs by those artists. Here are some screenshots to illustrate it.