The Cosmologies project aims to situate the listener inside a virtual grand piano by enabling computer processes to learn from the spatial presence of the live instrument and performer. We propose novel techniques that leverage measurements of natural acoustic phenomena to inform spatial sound composition and synthesis. Measured radiation patterns of acoustic instruments are applied interactively in response to a live input to synthesize spatial forms in real time. We implement this with software tools for the first time connecting audio descriptor analysis and corpus-based synthesis to spatialization using Higher-Order Ambisonics and machine learning. The resulting musical work, Cosmologies for piano and 3D electronics, explodes the space inside the grand piano out to the space of the concert hall, allowing the listener to experience its secret inner life.