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In Spain this progression was called "Guardame las vacas" because the locally-known song of that name used the same progression. This progression, eminently suited to variation, hovers between tonal and modal harmony. The V - i cadence at the end is quite tonal, but the iii - vii opening is modal. Taruskin makes the very interesting point that it was quite likely that tonality was long used in extemporized music before it was ever written down in the 16th century. Here is a performance of "Guardame" so you can hear how the progression is used:
As you can hear the chord progression is kept to exactly throughout except for the four-measure coda that ends the piece. All the variation is melodic using different registers and even the hemiola alternation between 6/4 and 3/2 is preserved though most performances fail to express it. This one does. If you are looking for a modern parallel to progressions like the romanesca, the obvious choice is the 12-bar blues progression. Here is an example:
The progression goes, with each chord symbol representing a full measure: I I I I IV IV I I V V I I. Over this a million guitarists, blues-harp players and others have improvised variations.
Perhaps the most astonishing set of variations using the idea of a repeated chord progression are the sublime Goldberg Variations of J. S. Bach. Instead of a simple four or eight measure progression Bach's is in two halves, each 16 measures, repeated:
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Bach, in his set of variations, synthesizes two different traditions: that of the age-old melodic variations over a repeating progression and that of the canon. A 'canon' is a rule and in music it means that one voice is a strict copy of another voice but starting later, or on a different pitch, or in different rhythmic values or upside down or backwards or some combination of these. The possibilities are both endless and challenging. One of the great historic examples is Johannes Ockeghem's Missa prolationem dating from the second half of the 15th century which is two double canons in an ascending cycle of intervals: at the unison, second, third and so on. The name of the mass comes from the fact that each voice sings in a different mensuration or prolation. Here is the Kyrie:
I recommend watching it in YouTube so you can read the score easily. As you can see, the top two voices are in canon, but can start at the same time because they are in different note values. A half note in the top voice is answered with a dotted half in the second voice. Similarly, a dotted half in the third voice is answered by a dotted-half tied to a dotted quarter in the lowest voice. Also note that the two pairs of voices are in canon at the unison. The Goldberg Variations by Bach use the repeating chord progression but overlays this with a series of canons, each at a larger interval. This does not rule out imitation in the other variations, of course. Here are the whole of the Goldbergs performed by Gustav Leonhardt on harpsichord with the first edition of the score:
The third variation is the first canon, at the unison, and begins at 5:17.
Now this has turned out to be a very long post and I haven't even gotten to Beethoven yet--much like the novel Tristram Shandy I have started to tell a story and ended up giving you nothing but digressions! Let me summarize: two of the most powerful compositional techniques used in the first millennium of music history were the repeated chord progression with melodic variations and the canon. Both techniques served to offer both unity and variety. Bach's Goldberg Variations are a superb synthesis of the two techniques. So there was really nowhere for poor Beethoven to go, right? Most composers have felt this, I'm sure, as they look back. "I'm at the end of music history--all the good stuff has already been done!" they cry out plaintively. But in fact, what makes Beethoven Beethoven is that he began an entirely new phase in music history by writing an astounding set of variations that, unlike Bach, make use of almost none of this historical background. So, my next post will look at exactly what Beethoven did do in his Diabelli Variations.