Rik is the ear, Sâman the mind. This Sâman (mind) rests on that Rik (ear). Therefore the Sâman is sung as resting on the Rik. Sâ is the ear, ama the mind, and that makes Sâma.

In plain words: The verse is like the ear and the song is like the mind, because the mind depends on what the ear hears. Sa is the ear and ama is the mind, and together they make Sama.