Question: how did she play the piano with jelly

Kate Mulcahy answered on 6 Jan 2015:

The jelly was connected to something called a Makey Makey. A Makey Makey is a small circuit board which allows you to turn objects into controllers. So instead of pressing a button on your keyboard to play the computer piano you can connect up the Makey Makey to anything that will allow at least a small amount of electricity to pass through it and touch these objects to play the piano.

In a basic circuit electricity has to travel in an unbroken circle. It can be connected to different things in the circuit but there always has to be a path for the electricity to flow in a circle.
In a Makey Makey circuit the person is connected to one part of the circuit and then an object is connected to another part of the circuit. When the person touches the object this completes the circuit and a small bit of electricity can flow through the person and the object.
Depending on which part of the Makey Makey is attached to the object when the electricity flows the computer receives a different instruction.
Each of the jellies was connected to a different part of the Makey Makey each of which was programmed to be a certain note on the piano.
Therefore any time Danielle touched the Jelly she was completed the circle for that note and the computer played the note.
When we were designing this we picked jelly because it is funny to watch but also because it is a good conductor of electricity but many more things can be used – I’ve even seen people playing animals!