A horizontal span of music that is played together. Most printed music displays systems spanning the full width of pages. A system can contain any number of staves. For example, in orchestral full scores, systems typically contain staves for all instruments in the orchestra, meaning a single system often occupies the full height of the page. In part layouts, each system only contains the staves required for that player, which is often a single staff and means multiple systems can fit on each page. See also system break, page break, casting off.