OnSong has the ability to divide your screen in a way that places menus on the left or right side while keeping your song full screen. We call this feature "Vertical Menubar" because it places the menubar along the side edges of the screen vertically, instead of along the top of the screen in other apps. You can learn more about the Vertical Menubar feature here: http://onsongapp.com/docs/features/vertical-menubar/
To enable vertical menubar, go into the Utilities menu by tapping on the gears icon in the upper right corner. Next, choose Settings > Menu Settings > Menubar > Vertical Menubar and turn this on: http://onsongapp.com/docs/interface/menubar/utilities-menu/settings/menu-settings/menubar/
By default, the menubar is placed on the left side of the screen. You can move it to the right side of the screen on iOS 11 and higher devices by toggling the "Reverse Menubar" option in the same setting screen. While this reverses the order of icons in the horizontal menubar, it places the vertical menubar on the right side of the screen when using vertical menubar mode.
The menubar appears on top of the song content underneath. To achieve a split-screen with the menu and full song displayed, tap on the "pin" icon at the bottom of the menu. This will redraw the display and pin the menu on the side with the song in full, unobstructed view.