Lines a Whole Step Apart, 3 Lines per Octave
From the Guided Tour: This system is similar to those with four lines, a whole step apart, but with a staff of only three lines alternating with three ledger lines per octave (instead of four and two). It is the least visually "dense" of the systems with staff lines a whole step Apart, and it requires the most ledger lines. Signs such as dynamic markings can be written in the space created by the ledger lines, even when multiple staves are stacked contiguously.
6-6 Trigram Notation by Richard Parncutt (1990)6-6 Trigram Notation by Richard Parncutt
The standard staff has two groups of three solid lines with groups of three ledger lines appearing above, below, and between them as needed. The three solid staff lines represent the group of three black notes on the piano keyboard (F#/Gb, G#/Ab, A#/Bb). The three ledger lines represent C, D, and E. Like Parncutt's other notation designs, the staff is aligned with the 7-5 pitch pattern, even though the lines and ledger lines have a 6-6 pitch pattern.
Earliest documentation: 1990
Source: Directory of Music Notation Proposals, section/page: 13/64
Similar Notations: Keyboard (or 7-5) Trigram by Richard Parncutt, 6-6 Tetragram by Richard Parncutt, Ambros System by August Ambros
