Ledger lines
Ledger lines are short lines that extend the staff upward and downward. Notes that do not fit on the five lines are written on them and between them.
They are read exactly like the staff: line, space, line. Each step is the next white key. The further from the staff, the higher (above it) or lower (below it) the note sounds. A ledger line is drawn only at the note itself, not across the whole line of music.
Below the treble staff: on the first ledger line is middle C (C4), below it B3, on the second ledger line A3. Above the treble staff: on the first ledger line A5, above it B5, on the second ledger line C6. On the bass staff the first ledger line above is middle C; below it, the first is E2 and the second C2.
When ledger lines pile up, reading gets hard. Then the notes are written an octave lower with the ottava sign 8va above them: play an octave higher than written. For far-away notes, count from the nearest landmark, such as the C on the second ledger line.
Where it is taught: the studio’s interactive textbook, chapter 1, “The keyboard and your first notes” and chapter 16, “Ledger lines and octaves”.