Sometimes, the older way of doing things is easier for people to use.

What happens when you have thousands of songs digitally encoded in iTunes or some other player? It makes for great random/shuffle playing, where you can let songs play for hours on end, and it works OK when you're sitting at the computer. However, how do you control the playback of such a collection in a relatively drunk-proof manner while you're holding a party, for example.

Well, you could add a cartridge-based juke-box style control system.

Using a PIC16F672 embedded in empty CD jewel cases, a group of friends created a system where each CD case represents a particular song or playlist. When the case is inserted into a specially modified receiver, several electrical contacts are made which allows the embedded PIC to communicate with a PIC18F452. Since each case-PIC microcontroller has a unique ID, the host chip can determine which "cartridge" has been inserted and then signal the computer which songs or playlist to change to.

They also added a multi-color LED into each jewel case which allows the system to display its various states using colors. One color shows which cartridge is playing, another color shows which one is next-up in the queue, and so-on. It's a pretty elegant, simple way to provide feedback to the users.

Overall, this isn't very practical since you'd have to build a custom jewel-case/embedded PIC for every playlist or group of songs you want to hear, which would be time-consuming, expensive, and as you know, those jewel cases tend to take-up lots of space when you have too many. Still, it's an interesting concept in combining modern digital music with an interface that your grandparents can probably understand.

Video below shows the PIC microcontroller-based juke-box interface in operation.