As discussed by Vitali, the single notated strophe follows the rubric Alleluia in natale apostolorum and is itself followed by a notated Alleluia with Verse appropriate to the dies apostolorum (29 June) i.e. Iam non estis ospites. The notated melody for the Alleluia and Verse follows the version edited from a twelfth-century German Gradual in Schlager’s catalogue of Alleluia melodies (Monumenta monodica VII, 252-3). The relation between Arbor natus and the Alleluia is not entirely clear. The rhythmical strophe is preceded by an A, presumably for antiphona, which in view of the lack of any introductory formula would appear to rule out any notion that the strophe was an introductory Alleluia trope. One possibility is that the strophe was sung as a processional antiphon and was followed by the Alleluia and Verse. The singing of Arbor natus in this context could be justified in terms of function, although there is no obvious thematic relation to the dies apostolorum. Here Vitali’s observation that Adam and Eve are invoked in a further ritmus (Schaller-Könsgen, 1362) concerning the lament of a wife abandoned by her husband, which is in this case the Apostle Peter, and that similar words to those are found in the second strophe of Arbor natus might well be significant. That the explicit association is through words quoted in the second strophe of Arbor natus, could also be taken to imply that more than one strophe was sung on the dies apostolorum: seven abecedary strophes are transmitted in the only other record of this poem, which remained unnotated.