The Guidonian hand. What it is and how it works.

I swear I tried to watch it, but the guy speaking is really hard to follow :-) anyway, you can find various explanations online about how the Guidonian hand works

Thanks Thallo, indeed I am struggling and was asking just what you think.

Can someone take a brief crack at it?

First of all, you must deepen your understanding of the Guidonian hexachord. Once this is clear to you, you will discover that Guido invented a mnemonic form to remember the exact intonation of the natural hexachord, i.e., the series of sounds forming a diatonic scale consisting of 5 intervals (TTSTT); to facilitate the mnemonic retention of this succession, Guido resorted to the initial syllables (ut, re, mi, fa, sol, la).

The hexachord was enriched in the 16th century by the note Si (to denote the VII degree of the scale), thus transforming it into an octave. One of the first musicians to practice the new system was Hubert Waelrant (1517-1595), who founded a music school in Antwerp in 1547.

Within the framework of Gregorian diatonic modes, three semitones are provided: mi-fa, si-do, and la-sib. The semitone is preceded and followed by two tones. This creates a sort of stable model, suitable for any modal context. Expanding the succession changes the interval ratios, which is why the "fixed" system is limited to the hexachord.

If the cantor memorizes the hexachord and the different interval relationships and combinations contained within it, they assimilate an intonational model applicable to different contexts: this involves always naming the semitone interval with the syllables mi-fa, even in the presence of the si-do and la-sib semitones. Therefore, the syllables designate an interval ratio and not the absolute pitch of the sounds.

This didactic device, based on the transposition of the hexachord, is called solmization, and for learning solmization, a device called the "Guidonian hand" was used (used between the 11th and 17th centuries): to each phalanx and fingertip of the left hand correspond a sound and one or more Guidonian syllables (starting from the thumb in a counter-clockwise direction).

The hand is reproduced in numerous medieval treatises subsequent to Guido (he makes no mention of it in his works) and was unduly attributed to him.

The hexachords were classified according to whether they included B-flat, B-natural, or neither of the two sounds:
• 3 hard hexachords: in which UT corresponds in absolute pitch to SOL (contained the B durum, B-natural)
• 2 natural hexachords: in which UT corresponds in absolute pitch to DO (contained neither B durum nor B molle)
• 2 soft hexachords: in which UT corresponds in absolute pitch to FA (contained the B molle, B-flat)
In the event that the melody to be intoned exceeds the range of the hexachord, one will resort to mutation, i.e., the syllables will be modified to "transfer" into the new sonic context and reapply solmization.
The principle of solmization was adopted in the last century by European educators such as Zoltàn Kodàly (Hungarian) and Roberto Goitre (Italian).

Annuccia, when one knows things, many words are not needed

A good music history text is enough for you anyway, thank Frank that he prepared the easy meal for you

Thanks Frank, it still remains a bit of an abstract discussion for me, but at least I have what appears to be a good summary to follow.