D. The "Middle staff" ("Alto staff" and "Tenor staff") of the Hexagram
: With two small parallel vertical lines together with the sign c (like M.-c),
one can represent the "Middle-c clef" ("Alto clef" and "Tenor clef"), which indicates
the position of the "Middle staff" between the two register systems of treble and bass in
the middle register, i.e. an octave lower than the "Treble staff" and one higher than the
"Bass staff", as in figures 12 and 13:
Figure 12) Position of the "Middle staff" register
Figure 13) Scale structure on the "Middle staff"
: The set of six lines, at once equal and versatile, applies to the middle
register between the registers of the "Treble staff" and "Bass staff".
: The range of notation has been expanded, the addition of ledger lines reduced
or avoided; the clef has been determined, and the reading of the notes unified. The
transition to other staves has been facilitated, making for ease of application.