The guts of the A-Team Egg are made up of only a few electronic parts. The brain is a Picaxe M08 microcontroller wich can be easily programmed to play music. The ability to make sound is already implemented in the chip. It is programmed in an easy BASIC dialect. As you can see in step 3 the code is only 5 lines long.
To make it "sing" you have to add a piezo speaker (it is also possible to add a speaker, but for the bleepy effect i use a piezo). To make it sensible for movements (shaking the egg) I added a tilt switch.
First of all make the Picaxe-08 Proto Board by following the instructions from Revolution Education
Then add the tilt switch between V (+5V) and Pin 4. You also have to solder the pull down resistor (10k) between Pin 4 and G (ground bus or 0V).
To connect the piezo speaker to Pin 2 I added a small wire between Pin 2 and the conducting path (see image). Then solder the piezo speaker between the path where the wire ends and G. Thats all for soldering. Easy, isnt it? Go to the next step to program the brain.