Grove's dictionary of music and musicians

500 SOLMISATION SOLMISATION
with our Diatonic Semitone, was its undoubted
homologue ; ' and throughout tlieii- system this
Hemitone oocuned between the first and second
sounds of every Tetrachord
;
just as, in our
major scale, the semitones occur between the
third and fourth degrees of the two disjunct
Tetraohords by which the complete octave is
represented. Therefore, they ordained that the
four sounds of the Tetrachord should be represented
by the four syllables, ra, re, -nj, tio ;
and that, in passing from one Tetrachord to
another, the position of these syllables should
be so modified, as in every case to place the
Hemitone between ra and re, and the two
following Tones between re and rrj, and rri and
Tu, respectively. 2
When, early in the 11th century, Guido
d'Arezzo substituted his Hexachords for the
Tetrachords of the Greek system, he was so fully
alive to the value of this principle that he
adapted it to another set of syllables, sufliciently
extended to embrace six sounds instead of foiir.
In the choice of these he was guided by a singular
coincidence. Observing that the melody of
a hymn, written about the year 770 by Paulus
Diaoonus, for the festival of St. John the Baptist,
was so constructed, that its successive phrases
began with the six sounds of the Hexachord,
taken in their regular order, he adopted the
syllables sung to these notes as the basis of his
new system of Solmisation, changing them from
Hexachord to Hexachord, on principles to be
hereafter described, exactly as the Greeks had
formerly changed their four syllables from Tetrachord
to Tetrachord.
C sol-fa-ut