This collection includes three masses: the _Missa della Domenica_, _delli_ (sic) _Apostoli_, and _della Madonna_, each one consisting of a Toccata for a prelude, of the versets of the Kyrie, and of pieces written to correspond to the various portions of the office, suitably designated; thus (p. 49), _Recercar cromaticho post il Credo_, or (p. 77), _Canzon dopo la pistola_ (sic). The versets of the Kyrie, in the three masses, are for the greater part more properly "Ecclesiastical songs without words," as Ambrose said, than compositions of a purely instrumental character; in fact, they are written strictly within the compass of the voice, and only the long duration of single notes (as in the alto on page 7, or in the soprano on page 8) precludes the possibility of their being sung. Curious is the effect of the pedal notes, sustained from the beginning to the end of a verse; and we find remarkable examples of a polyphonic accompaniment to the text, doubly interesting because of the continual reappearance of the theme, either in its integrity or slightly modified. Further, while making use of the accidentals required by the modulation of the parts in the counterpoint, and especially in cadences, Frescobaldi respects as much as possible the diatonic character of the Gregorian scale; he adheres to it with as little variation as possible, particularly when he brings it into prominence. The mode, the Dorian, remains uppermost in the mind of the auditor, and the counterpoint is most often derived from the same tone, sometimes in imitation, at others in ingenious inversions of the melody which it accompanies. One of the more elaborate of these versets, the _Kyrie ultimo_ of the _Missa della domenica_, ends with an allegro, a veritable _alla breve_.[14] [Footnote 14: With Frescobaldi we find no final cadence other than a perfect major; at his time the idea of a major or minor tonality was still to be conceived, and even for a long time after this distinction was finally made the custom prevailed of ending a piece written in a minor key by a major chord. Thus, in a collection of 371 chorales by J.S. Bach, of which 113 are in the minor mode, 108 of the latter end with a major chord.] If in nature these versets partake somewhat of the character of compositions for voices, we find in other numbers of the _Fiori musicali_ a very close affiliation with vocal music. We refer to that grace and flexibility of proportion which prompts us to say of this theme, of that counterpoint, "It is musical!" Especially in the _canzoni_ do we find these expressive qualities. It is well known that the instrumental fugue was born of this species of composition, which was also called _canzon francese_; the responses to a subject, sometimes of popular origin, and most often in this rhythm (a traditional one): [Music] became answers, and the alternation of double with triple rhythm gave rise to the fugue in several movements, such as Buxtehude, in particular, often wrote.