 The use of "fa", "sol" and "la" for two positions in the scale is a leftover from the Guidonian system of so-called "mutations" (i.e.changes of hexachord on a note, see Guidonian hand).This system was largely eliminated by the 19th century, but is still used in some shape note systems, which give each of the four syllables "fa", "sol", "la", and "mi" a different shape.