The “Climate Action Wall” was a minimal intervention to spark public participation at The ClimateMusic Project’s “Play for the Planet” event. “Play for the Planet” was a one-day event performed live on the steps of the San Francisco Public Library, featuring a diverse array of musicians and performers who were asked to respond to the prompt: “What do we want our future to sound like?” “Play for the Planet” featured melting ice sculptures by artist Carter Brooks, and hosted several walk-on performers from the surrounding neighborhood. Listeners were offered a card to share a personal pledge to take a climate action – or to share a climate action they are already committed to – and add their card to the “Climate Action Wall”. The wall was a way of testing a public participation activity using very simple, affordable tools and materials. The ClimateMusic Project creates original musical pieces created by transforming complex climate data into sound, and arranged the “Play for the Planet” event to build on energy and activities surrounding the Global Climate Action Summit taking place in San Francisco the same week (September 2018).