This view is a visual guide to help match the sound's pitch to standard keys, or, in the infra-bass section of the score, match the pitch to a tempo indicator, measured in bpm (beat per minutes). In a future version, pressing on a key will let you hear a sample at their corresponding pitch or beat.
You can show or hide the keyboard view with the Tools > Keyboard action.
Those include: the tag manager, the piece inspector, the view inspector, and the messages window.