Johnston–Copper notation

Based on Johnston's ideas but extended by means of key signatures, this is the notation used by William Copper in the works composed by the techniques of intonalism

Johnston takes as a just intonation basis the staff notation without accidentals (white keys on the piano) so that there are three 4:5:6 chords (F major, C major, and G major). Copper extends this system so that the same three 4:5:6 chords are transposed according to a key signature. In the key of C major, the Johnston and Copper systems are the same. In the key of one sharp, G major, the three 4:5:6 chords are changed so that the basis of just intonation becomes C major, G major, and D major. Any note found in this basis and not altered by a special accidental is tuned according to 5-limit just intonation: the third of the triad, or the '5' of the 4:5:6 chord, is a pure major third from the root; the fifth of the triad is a pure perfect fifth from the root.