In the examples you've provided, the one that qualifies as tangible property is "a quicker system of washing the car that you thought of last Summer."
Tangible property refers to physical items that can be touched or physically measured, whereas the ice cream method, unrecorded ideas, and song lyrics are more abstract or intellectual property concepts. The car washing system, depending on its specifics, could involve tools or methods that can be developed into a physical product or service, making it a tangible property.