the counterpoint should crystallize. This 'subject,' or parts of it, was used over and over in the successive movements of a mass, supplying in the tenor a fixed nucleus more or less familiar, while the ingenuity of the composer consisted in adjusting to it manifold figures and phrases in the other voices, occasionally in imitation.
In consequence, masses were known by the titles of their 'subjects,' as
the Mass L'omme armé or Se la face ay pale (popular songs used in unnumbered instances), or Eloy's Mass Dixerunt discipuli (from Plain-Song). Later, practice-phrases from the singing-school were similarly used, as in Des Près' Mass La, sol, fa, re, mi.
It should be added that this practice of mixing words and styles seems to have been one of the early characteristics of the form known as the 'motet' (see sec. 55).
Not only were the tunes of well-known songs thus incorporated,
but in many cases their words were actually sung by the
tenor while the other voices were proceeding with the prescribed
Latin text—a practice so open to abuse, especially
when frivolous or immoral thoughts were suggested, as to call
out in the 16th century the formal rebuke of the Church. In
the beginning, however, this free use of secular materials in the
most solemn works was not irreverent, but simply a token of
the source whence the whole style of writing came.
Here is a suitable place to state once for all that wherever a musical
'mass' is mentioned, it includes only those specific exercises in the
liturgy that are traditionally assigned to the choir, acting as an auxiliary
to the officiants at the altar. It does not include any of the many passages
recited or intoned by those officiants themselves—these being in
Plain-Song. Neither does it properly include any variable parts of the
service, the text of which depends upon the day or the season—these
being rather 'motets.'
The invariable choir exercises include (a) the Kyrie eleison or general cry for mercy that follows the Introit, (b) the Gloria in excelsis immediately succeeding, which is often divided into distinct sections, beginning respectively with the words Dominus Deus, Qui tollis, and Quoniam tu solus, (c) the Credo or Nicene Creed, usually divided into sections at the words Incarnatus est, Crucifixus, Et resurrexit, and Et in Spiritum Sanctum, (d) the Sanctus, with the Hosanna, before the Elevation, (e) the Benedictus qui venit, after the Elevation, and (f) the Agnus Dei, at the Commixture, the latter part of which, the Dona nobis pacem, being often treated by itself. To these are often added a setting of the Gradual, the hymn intervening between the Epistle and the Gospel, and of the Offertorium, the hymn following the Credo—both of these being variable. There is an obvious difference of intention in the various num-
