By
Luis Torres Zuleta
© Canticum Novum
Bogota, Colombia2003

The second stage of the rhythmic synthesis consists on the formation of groups. The groups are formed with base in compound times. The compound times are groups of two or three simple times, starting from the marked sounds with a vertical episemata; they receive the name of binary or ternary, respectively. They are equal to tempo of 2/8 and 3/8 in modern notation (1)

binary compound time	ternary compound time

Each one of these compound times, in their entirety, can be arsis or thesis of a rhythm.

To determine what compound times are arsic and what compound times are thetic, the factor that have most influence is the melodic ascent or descent. This way, the upward melodic turns are prone towards an impulse character, while the descending melodic turns have character of rest.

Examples of arsic compound times :

	The third compound time, although begins with a descent of second, goes to ascend a third immediately.
	The first compound time, although begins with a descent of second, goes to ascend toward a fifth.

	The third compound time, although begins with a descent of third, goes to ascend a fourth immediately.
	The arsic compound time arrives with descent of third to ascend toward a fifth.
	The arsic compound time arrives with descent of second to ascend a fifth immediately.

	To stand out the sound lengthened by horizontal episemata.
	To stand out the sound lengthened by horizontal episemata.

The repercussions that are going to approach to a higher sound are of arsic tendency.

Examples of thetic compound times:

The repercussions that appear after higher melodic turns are of thetic tendency:

Indifferent compound times:

If the compound times are succeeded by sounds that are to the same height, they are indifferent, as for their character. However it shall be the text the one that motivates a definition, with base in the natural rhythm of the words.

Notice: The Latin words have a natural rhythm, by means of which the united syllables, of two in two, starting from the thetic syllables, form unions with arsic character that have as thesis the final syllable of the word.

Paroxytonic accented words	Proparoxytonic accented words

(2)

	The arsis and the thesis are defined by the natural rhythm of the proparoxytonic accented tri syllabic word.
	The arsis and the theses are adjusted to the natural rhythm of the tri syllabic proparoxytonic accented words and exasyllabic word of the text.
	The arsis and thesis pointed out here are adjusted to the natural rhythm of the tri syllabic paroxytonic accented word.

There are indifferent times by their self that take also their characterization with base in the rhythm of the words.

These compound times would be thetic if, instead of being in the accented syllable, they are in a final syllable of the word, as it happens in the following example:

(3)

Observation:
Although, the factor that conditions more the character of the compound times is the melodic ascent or descent, what above all should be looked for is the sense of impulse or rest in each moment; this gives some space for personal appreciation.
In the following examples there are arsis and thesis that contradict the melodic ascents and descents.

Group:

	Two binary compound times.
	One binary compound time and one ternary.
	One ternary compound time and one binary.
	Two ternary compound times.

Extended Group

When a group is formed by more than one compound time, either as arsis either as thesis, it is called an extended group:

	One compound time as arsis and two as thesis.
	One compound time as arsis and two as thesis.
	Two compound times as arsis and one as thesis.

	Two compound times as arsis and one as thesis.
	Two compound times as arsis and two as thesis.
	Three compound times as arsis and two as thesis.
	One compound time as arsis and three as thesis.

When the piece begins with a thetic compound time, there is total elision of the compound arsic time of the rhythm; this is enough to consider it as a binary one:

When the piece begins with a simple time, there is a partial elision of the initial arsic compound time, that is to say of only one simple time:

The great dividing bar can be part of a thetic compound time:

Small, medium and even the biggest dividing bars can be located among the sounds of a compound time:

When in a succession of paroxytonic accented words, the rhythmic weight relapses in the accented syllables, the compound times form rhythmic relationships:

The groups and extended groups are succeeded in multiple combinations. The appearance of an arsic compound time after a thetic one means the beginning of a new group:

_________________

(1) Jachino, Carlo. Ritmo musical, Enciclopedia italiana, Vol. XXIX, pág. 460, Nº 12.
Riemann, Hugo. Composición musical, primera parte, cap. I, pág. 29.

(2) Martínez Soques, Fernando. Método de canto gregoriano. Cap. XIV, pág 147 y ss. Ed. Pedagógica, Barcelona, 1943.

(3) Martínez Soques, F. Op. cit. cap. IV, Nº 38, pag. 46

(4) Riemann, Hugo. Composición musical, Cap. III, págs. 138 y ss. Ed. Labor S.a., Barcelona, 1929

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