For the purpose of introducting children to various melodies, learning to order things by sound and just for fun, consider this musical table by Instructables user "indistructableBubble". It's a clever interactive system, that uses two Arduino boards to play various tunes depending on the type of robot that is inserted into one of four trapezoidal holes in a table. This works by having four contacts in each hole - with each robot having a different pattern of contacts on the base ... so when each on is inserted into the hole it is recognised by the Arduino and the matching tune played - for example:
Certainly something different and fascinating, including the robot recognition system - so visit the Instructable for more information. And for more, we're on twitter and Google+, so follow us for news and product updates as well.