Keyboard musical instrument with laterally-adjustable, built-in musical rack

A grand piano has a built-in music rack (7A) for keeping a music score book (13) thereon, and the built-in music rack (7A) includes a guide (20/ 25) laterally extending inside the piano cabinet (2A) and a desk board (7b) projecting over the piano cabinet (2A) and connected to the guide; when a pianist exerts force on the desk board (7b), the guide (20/ 25) permits the desk board (7b) to slide laterally so that the pianist can easily adjust the music score book (13) to a proper position; since most of the guide (25) is hidden inside the piano cabinet (2A), the pianist feels the grand piano same in external appearance as a standard grand piano.