The figures on the upper archivolt seem to represent, for the most part, monsters derived from classical mythology. Here and there, however, we can identify a literary allusion, as with this ass musician. It is noteworthy that while in the original fable, the animal played a fiddle, or bowed string instrument of some sort, here it plays a harp. The replacement of harps by rebecs and vice-versa which we observe on this portal is perhaps due to the demands of perspective: whereas the rebec is the more successful of the two in a frontal representation, the harp lends itself perfectly to a profile view.