The extreme antiquity of the piece would alone make it an object of reverent interest, for it is the earliest example of a canon, it is the first recorded use of the ground-bass or _basso ostinato_, and it is the only known piece in six real parts before the fifteenth century. But the wonder grows when we consider the musical quality of this remarkable melody of unknown parentage, ‘born out of due season.’ It is sweet and joyous in character, fitting the pastoral mood of the words; it flows along in graceful outline with a wonderful amount of melodic variety; it maintains an easy rhythmic swing in definite three-pulse measure; it has an unmistakably modern feeling for key--the key of F major--made all the more definite by clearly defined tonic and dominant harmonies which pulsate back and forth in alternate measures. In musical feeling and expression it is ‘immeasurably in advance of any polyphonic music of earlier date than the Fa-las peculiar to the later decades of the sixteenth century’ (Rockstro). Its formal structure displays full knowledge of the contrapuntal devices of the times and also remarkable freedom in handling them. The apparition of this warm-blooded melody amid the arid scholasticism of the thirteenth century seems utterly incongruous. Yet Rockstro’s explanation[13] seems plausible enough. He points out that some folk-songs of greatest antiquity possess the same qualities of ingenious grace that shine so resplendently in this melody. The words are evidently Northumbrian; what could be more natural than that some trained monkish ear caught the melody and words as they fell from the untutored but inspired lips of some north-countryman, rubbed off a rough place here and there, detected its adaptability for use as a ‘round’ theme (a quality quite common in folk-songs), and worked it out with his clerical companions in extempore fashion after the custom of the times?