I copy this from DrCanadianNinja
After unlocking the second mix for Blue Monday, the Motherboard opens up. You can only send a charge through one side of the circuit board at a time, at which point the opposing side opens up and you can send it back.
What you want to do is send all charges to one side, then start a figure eight. Activate all charges swiping down, swipe up the middle, down to send the charges the other way, swipe up the middle, repeat. Your goal is to get the charges trapped in the middle, playing the same two or three notes. A circle won't work, as the top or bottom charges will finish in the meanwhile.
Once you get the proper rhythm going, it unlocks in ten seconds.