which, in accordance with the well-known laws of Hebrew Poetry, the Verses of the Psalms are often divided, while, in nearly every case, the final Cadence, or 'Ending,' is invested, for the sake of variety, with several different forms. The First, Third, Fifth, and Seventh Tones, representing the four Authentic Modes, are represented by tradition to have been the only ones used by S. Ambrose [see Modes, the Ecclesiastical"); and to these, S. Gregory is said to have added the Second, Fourth, Sixth, and Eighth, each written in a Plagal Mode: but more than one writer on the subject is of opinion that these last-named Tones were in common use long before the time even of S. Ambrose. [See Plagal Modes.] It is, in fact, impossible to trace back the eight familiar forms to the time of their first adoption into the Services of the Church; and still more so, to account for the origin of a supplementary form, which, though unquestionably written in the Ninth, or Æolian Mode, is uniformly described, not as the Ninth Tone, but as the 'Tonus Peregrinus.' [See Tonus Peregrinus.]
Every Psalm and Canticle sung in the Divine Office is accompanied by an Antiphon, which, on Festivals, precedes and follows it, but, on Ferias, follows it only. Antiphons, selected from Holy Scripture, and other sources, are appointed for every Feast, Fast, and Feria, in the Ecclesiastical Year; and each is provided with its proper Plain Song Melody, which will be found in Antiphonarium Romanum.' It is indispensable, that, in every case, the Psalm and Antiphon should be suug in the same Mode; the Tone for the Psalm is therefore suggested by the Mode of the Antiphon; and, as the Psalm Tones—if we except the Tonus Peregrinus, with which we are not now concerned—are written in the first eight Modes only, it follows that the Melodies proper to the Antiphons must necessarily conform to the same rule. Some of these Melodies are extremely beautiful. They are of later date, by far, than the Psalm Tones, and much more elaborate in construction; but they are, none the less, models of the purest Ecclesiastical style. [See Antiphon.]
Next in importance—and, probably, in antiquity also—to the Psalm Tones, are the Inflections used for the Versicles and Responses proper to the Liturgy and the Divine Office; such as the 'Deus in adjutorium' at Vespers, the 'Dominus vobiscum,' and 'Per omnia sæcula sæculorum,' in the 'Ordinarium Missæ,' and other similar passages. All these are exceedingly simple, and bear strong evidence of very high antiquity. [See Responsorium; Versicle.]
Intimately connected with them are the various Accents which collectively constitute the 'Tonus Orationis,' the 'Tonus Lectionis,' the 'Tonus Capituli,' the 'Tonus Prophetiæ,' the 'Tonus Epistolæ,' and the 'Tonus Evangelii.' Each Accent is, in itself, a mere passing Inflection, consisting of two, or at most three notes; but the traditional commixture of the various forms gives to each species of Lection a fixed character which never fails to adapt itself to the spirit of the text. [See Accents.]
More elaborate than any of the forms we have hitherto described, and, no doubt, of considerably later date, are the Melodies adapted to certain portions of the Liturgy, which have been sung at High Mass from time immemorial. We shall first discuss those belonging to the 'Proprium Missæ'—i.e. that part of the Mass which varies on different Festivals.
The first, and one of the most important, of these, is the Introit; which partakes, in about equal degrees, of the characters of the Antiphon and the Psalm Tone. The words of the Introit are divided into two portions, of which the first is a pure Antiphon, and the second, a single Verse of a Psalm, followed by the 'Gloria Patri,' after which the Antiphon is again repeated in full. Except that it is perhaps a little more elaborate, the Melody of the first division differs but little, in style, from that proper to the Antiphons sung at Lauds and Vespers; and, for the reasons we have mentioned in speaking of these, it is always written in one of the first eight Modes. The Verse of the Psalm, and its supplementary 'Gloria Patri,' are sung to the Tone which corresponds with the Mode of the Antiphon; but, in this case, the simple Melody of the original Chaunt, though permitted to exhibit one single 'Ending' only, is developed into a far more complicated form, by the introduction of accessory notes, which would be altogether out of place at Vespers, when five long Psalms are sung continuously, though they add not a little to the dignity of this part of the Mass. The Antiphon is then repeated exactly as before, care being taken to sing it in a style which may contrast effectively with the preceding Chaunt; and, in Paschal Tide, this is followed by a double Alleluia, of which eight forms are given in the Graduale, one in each of the first eight Modes. [See Introit.]
The Gradual, though consisting, like the Introit, of two distinct members the Gradual proper, and the Versus—differs from it in that no part of it is recited, after the manner of a Psalm, upon a single note. The Melody, throughout, bears a close analogy to that of the more elaborate species of Antiphon, as exhibited in the first part of the Introit: and its two sections, though always written in the same Mode, are quite distinct from each other, and never repeat the same phrases. [See Gradual.]
On Festivals, the Gradual is supplemented by a form of Alleluia peculiar to itself, which, in its turn, is followed by another Versus, wherefrom it takes its Mode, and after which it is again repeated, after the manner of a Da Capo. This Alleluia is twice repeated, and then echoed, as it were, by an elaborate Pneuma, in the same Mode. [See Pneuma.] The style of the Versus corresponds exactly with that of the Gradual; and, after that has been sung, the Alleluia and Pneuma are repeated as before.
Between the Seasons of Septuagesima and Easter, the Alleluia, and Versus, are omitted,
