I play music and voices but have no voice of my own. What am I?

I run all the time, but never move a foot. I have a mouth, but never make a sound. What am I? Solve the riddle → I have legs but cannot walk. I have a flat back where things often rest. Solve the riddle → I have only one button, but I can change how a room looks. When it's dark, I work best, because I love to light things up. What am I? Solve the riddle → I have many keys, but I open no locks. You use me to type. What am I? Solve the riddle → You have me by your ears. I play music just for you. What am I? Solve the riddle →