Plain Language Summary Volcanic craters are like giant musical instruments in the sense that the sounds that volcanoes produce can change as the crater size evolves. We track the changing tones and resonance of low-frequency infrasounds at Volcan Villarrica (Chile) and attribute their variations as a response to the rise of the lava lake in the crater. We use infrasound data and employ numerical models to track the depth of the lava lake over time. Significant changes in infrasound character occurred just prior to a violent 3 March 2015 eruption leading us to propose that monitoring volcano infrasound resonance is important for forecasting future volcanic eruptions.