Now, you’re ready for mass production !
Just kidding, this set is an eye catcher, well done !
I recommend using strong neodymium magnets underneath each cube to make a sturdy construction.
For the ground connection, you can use these magnets for contacts. Some of them have small eyelets where you can attach a wire using a bolt and nut.
Did you use a special earphone ?
I would love to see a circuit build with this set.