 Although ledger lines are found occasionally in manuscripts of plainchant and early polyphony, it was only in the early 16th century in keyboard music that their use became at all extensive .Even then, printers had an aversion to ledger lines which caused difficulties in setting type, wasting space on the page and causing a messy appearance.Vocal music employed a variety of different clefs to keep the range of the part on the staff as much as possible; in keyboard notation a common way of avoiding ledger lines was the use of open score on four staves with different clefs .