Automatic Scrolling During Playback
During playback, Composer automatically scrolls the window vertically and horizontally to show the current position in the song. It scrolls horizontally a few extra beats ahead of the current playback position so that you can see the notes ahead. Composer also turns the page a few beats ahead of the current playback position. You can specify the exact number of beats for the page turn anticipation.
If Composer's window is not tall enough to display all of the staves for the current measure, then Composer automatically scrolls the window vertically to a position that maintains the focus on some staff that you have selected, or which otherwise Composer selects by default. You can assign playback focus to a staff, thus setting the playback staff marker, by clicking the staff while you hold down the "V" key (for "vertical focus").