A music box is a mechanical device that plays musical tunes when a handle is turned. The three letter answer, AMP, stands for Amplifier, which is an electronic device used to increase the volume of sound. The four letter answer, IPOD, is a brand of portable media player developed by Apple Inc. The six letter answer, CDCASE, stands for Compact Disc Case, which is a storage container for CDs. The last six letter answer, STEREO, is short for stereophonic sound, which is a method of sound reproduction that creates an illusion of directionality and depth.