1c. Phrygian

The Gregorian Hymn Pange Lingua is in the 3rd church mode with respect to the octenary system of modes.

The pseudo-classical term "Phrygian" refers to a theoretical abstraction, which among other things involves a diatonic species of the octave with the step interval pattern S T T T S T T (S = semitone, T = tone).

With respect to relative Solmization this Phrygian mode is based on the syllable mi as its final/tonic. As a first exercise you may play and solmisate the melody with respect to this mode. You select "E-Phrygian" and start playing on the first scale degree (c.f. first part of the movie).

The characteristic semitone above the final occurs at the beginning and at the end with the syllables mi and fa. The other semitone between scale degrees 5 and 6 occurs several times in the middle of the melody. It comes with the syllables ti and do.

In Medieval solmisation, however, the syllable ti was not available. Solmisation was based on hexachords (with syllables ut re mi fa sol la). Every semitone had to be solmisated with the syllables mi and fa. Therefore in a second exercise you may play and solmisate the melody without using the syllable ti. The natural hexachord C-D-E-F-G-A covers the tones E-F-G-A as well as the tone D below the final E (see 5th and penultimate note). The hard hexachord G-A-B-C-D-E covers the remaining notes. The mutation between the two hexachords may be "technically" accomplished by switching between the E-phrygian and E-aeolian modes. But this just a technical trick on the Solfa-Mode-Go-Round (see second part of the movie). Hexachord-mutation should not be confused with a change of the mode.