Ledger line facts for kids
A ledger line is a short line used to write notes which would otherwise be too high or too low for the staff. A short line (slightly longer than the note) is drawn parallel to the lines on the staff, and the note head is placed on that line or in the space below or above it.
Notes with at least three or four ledger lines are rarely used for composing and arranging. It is easier to change the clef or use the “8va” sign (called "ottava" sign).
The piccolo always sounds an octave higher than the music written and the double bass always sounds an octave lower than written. Some wind instruments also transpose up or down an octave to make it easier to read, e.g. the bass clarinet sounds a ninth (just over an octave) lower than the music which is written in the treble clef (this makes it the same fingering as the clarinet).
Ledger line Facts for Kids. Kiddle Encyclopedia.