A number of notation designers have used a five-line chromatic staff
with one ledger line. This is a total of six lines spanning an octave,
each spaced a whole step apart. The ledger line allows multiple
one-octave staves to be “stacked,” placed contiguously for
greater pitch range. In many cases these staves look exactly like the
traditional staff (which would cause confusion), but some systems
introduce bold lines or change the position of the ledger line.