“Water Music”, anyone?
YouTube video posted by LittleScale, who also provided this explanation at the sidebar:
A slightly more complex version of using a water surface as a music controller featuring five lasers instead of just the one. Please note that this is a prototype version, and as such does not represent the variety of output for the finished thing.
Here’s his earlier setup, which is equally instructional.
A cheapo laser pointer, a solar panel and a clear vase filled with water are transformed into a music controller. Includes demonstrations of amp modulation, amp and freq mod and a more complex mapping as well.