[85] Imitation is _strict_ when the succession of intervals is identical in both antecedent and consequent; _free_ when some modification of the one appears in the other. Imitation is called _augmented_ when the rhythmic value of the several tones is systematically increased, as, for example, when quarter-notes are represented by half-notes; _diminished_ when the rhythmic value of the several notes is lessened; _inverted_ (or imitation in contrary motion) when every upward interval in the antecedent is represented in the answer by an equivalent downward interval, or vice versa; _retrograde_ (or reversed imitation) when the intervals of the antecedent are taken in the reverse order in the consequent. A _canon_ is a composition in which imitation is carried out at some length. Imitation is also the basis of the _fugue_. [86] It is in Walter Odington’s treatise that the first mention of duple metre is made. [87] Similar intervals occurring between two voices that pass from one chord to another in parallel motion. [88] A sequence of chords at the end of a phrase or period, involving, in modern music, a clear enunciation of the tonality or key in which the piece is written. Full, perfect, complete or authentic cadence is the dominant harmony in root position followed by that of the tonic in root position. This kind of cadence is comparable to a period. A half cadence is a less definite closing, used for phrases not final. [89] W. S. Rockstro, in Grove’s Dictionary, III, 259. [90] Quoted from an extant letter of Philip of Luxembourg to the Chapter at Cambrai. [91] 'Dufay and His Contemporaries.’ [92] Grove: 'Dict. of Music and Musicians.’ [93] 'Early English Harmony’; Vol. I edited by H. E. Wooldridge, 1897; Vol. II edited by Rev. H. V. Hughes, 1913. [94] See Chapter X. [95] The form Ockenheim was introduced by Glarean, apparently without sufficient reason. It is supposed that Okeghem was born about 1430. [96] 'Life of Palestrina,’ Rome, 1828. [97] Hullah: 'Lectures on the History of Modern Music,’ p. 53. CHAPTER IX THE ITALIAN RENAISSANCE Spirit of the Renaissance--_Trovatori_ and _cantori a liuto_; The Florentine _Ars nova_; Landino; _caccia_, _ballata_, madrigal--The fifteenth century; the Medici; Netherland influence; popular song forms--Adrian Willaert and the new madrigal--Orazio Vecchi and the dramatic madrigal.