Because I can. That's the only reason.
This was made using a custom app I created with the Unity game engine. I had the idea for a Bass Xylophone and built it with a fish model and a simple script that scales the fish up and places it along a track like Xylophone bars.
You can play the Xylophone with a mouse or on touch device, but I'm not very good at playing the Xylophone so I got a Creative Commons MIDI file and the rest is history.