When the singers sang solos, they ornamented the songs and sang anything they pleased! This made variety but it must also have caused much confusion! The people may have learned this ornamental singing of the Arab, from _The Gloss_. (Page 59.) The next step was the Gregorian chant which even today is sung in the Roman Catholic Churches. To the four authentic scales of St. Ambrose, St. Gregory who was Pope from 590 to 604 added four more called _plagal_. He did not invent these scales but based them on the old Greek and Ambrosian modes. To each authentic scale, he added a plagal scale starting four tones below it, and to the name of the authentic mode is added the prefix _hypo_. Each authentic mode and its _hypo_ are related. Here is a table of these related modes, and their names: [Illustration: _After a painting by Garofalo, National Gallery at Rome._ _Saint Cecilia—Patron Saint of Music._ (_Holding a portative organ._) ] [Illustration: _After a painting by Maxence, in Paris._ _Book of Peace._ ] AUTHENTIC SCALES OR MODES PLAGAL SCALES OR MODES (St. Ambrose’s Scales) (St. Gregory’s Scales) I. Dorian: II. Hypo-Dorian: d ef͡ g a bc͡ d a bc͡ d ef͡ g a III. Phrygian: IV. Hypo-Phrygian: ef͡ g a bc͡ d e bc͡ d ef͡ g a b V. Lydian: VI. Hypo-Lydian: f g a bc͡ d ef͡ c d ef͡ g a bc͡ VII. Mixo-Lydian: VIII. Hypo-Mixo-Lydian: g a bc͡ d ef͡ g d ef͡ g a bc͡ d We have marked the half-steps _bc͡_ and _ef͡_, and in every mode they fall on different degrees of the scale. This shifting of the half-steps tells us the name of the mode. In order to try to give you a definite idea of how the church modes worked, we have written the familiar national hymn _America_ in each mode (see page 74). Play them, and you will see how one differs from the other. Katherine Ruth Heyman has used a similar idea in her little book _The Relation of Ultramodern to Archaic Music_ in explaining Greek Modes. It took many years to establish this music and it was not until the time of Charlemagne (742–814) that it became a real system called Plain Chant or Plain-song (from the Latin, _cantus planus_).