The MUNCHKIN Mozart Magic Cube is a poor-quality copy of the original EMBRYONICS Mozart Magic Cube.
My guess is that Munchkin bought out the rights to this toy from the original manufacturer, which went out of business, then "redesigned" it more cheaply. While keeping the overall shape and function the same, they changed the outside colors, and the inner workings as well.
My older son received an Embryonics version in 2004, and we all loved it dearly until its battery cover broke. My younger son received the Munchkin version as a replacement gift, and we have all been sorely disappointed. The sound quality is horrible--the Munchkin cube sounds squeaky, tinny, and ridiculous, especially compared to the Embryonics version (which wasn't perfect, but much, much better).
You can still find the older Embryonics version online. It has all yellow sides, the buttons are printed with different colors, the edges and corners are all purple, and it has the name...