The staff has a 7-5 line pattern with each line or ledger line representing one of the seven notes of the C major scale (the white keys on the piano: A, B, C, D, E, F, G). The three fully visible lines represent the notes C, F, and G (the notation is also known as “C-F-G” notation). These notes are the 0, 5, and 7 pitches in the chromatic scale when starting with C as 0. The five other notes (the black keys on the piano) appear on spaces. As there is no black key on the piano between E and F or between B and C, there is no space on the staff for notes between the lines E and F or the lines B and C. These two pairs of lines are closer together. Traditional rhythmic notation is used.
Earliest documentation: 1984
Source: Directory of Music Notation Proposals, section/page: 10/20, 11/5, 13/62