ledger line

これまで読んできたMusic Theory for Dummiesに出てきた音楽用語に対応する日本語は知っていましたが、次の文に出てきた単語に対応する日本語は知りません。
If composers had to write guitar parts at their actual-sounding pitch, they would have to use too many ledger lines and the part would be confusing.
この "ledger lines" の意味を辞書で調べます。
・Oxford English Dictionary: A short line added for notes above or below the range of a staff.: In bar 194 of the Adagio, the Bass tuba has a low note with many ledger lines.
・Dictionary.com: Also, leger line. Also called added line. Music. a short line added when necessary above or below the staff to increase the range of the staff.: The compass extends from F below the bass staff to C on the second ledger-line above the treble.
・OnMusic Dictionary: The short, horizontal lines added to the top or the bottom of a staff for the indication of notes too high or too low to be represented on the staff proper.
英和辞典で見るとこれは加線と呼ばれるそうです。知りませんでした。