The Hertzian Collective is a musical sound game/toy created with projected video images played collectively by viewers on their mobile phones. The installation uses visual rhythms and spoken text to explore schoolyard games, inviting visitors to take control of the action or another through dialing a toll-free phone number and pressing buttons on their keypad. This interactive art piece was developed by Geoffrey Shea at the Mobile Experience Lab at the Ontario College of Art & Design with software development by Rob King using Twilio, which simplified the complexity of the project and made it accessible to a wide range of devices. The app took about six months to build and incorporates elements from other Mobile Lab works and the artist's own music projects, allowing visitors to jam and collaborate in real-time.