Music Rings are objects in Ecco Junior which need to be guided to empty rings to be set in place. When all the rings are set the song of the seas can be heard by swimming through all the rings fast enough. They make a chiming sound when swam into.
There are three colours, bronze, silver and gold, though only bronze and gold are used. Silver was presumably for a level that never made it to the final game, as only one silver ring appears in The Enchanted Sea where it serves no purpose.