Theo was digging in the box of cat toys I keep underneath the piano bench in the living room. Diego-san was sitting on top of the piano (one of his favorite spots to sit). I could tell by his posture and the way his tail was wagging what was on Diego's mind.
He was going to pounce on the unsuspecting Theo. But in order to get to a better spot for the pounce, Diego-san had to climb down lower. This meant he had to walk across the keyboard. As soon as he did so I assumed the Bartok like music would startle Theo- who was lost in the world of cat toys.
But the noise/alarm didn't even cause Theo to look up. Diego kept trying to find the ideal pouncing position and kept walking across the keyboard. Theo slowly strolled away, seemingly unaware of what he had somehow managed to escape. Diego went back to his spot on top of the piano.