The basic question of the paper is, whether the medieval institutions can be identified by the means of musical analysis. Two series of examples are documented, variants with clear characteristics. In the first series the same antiphon text is associated with two or more tunes; in the second series the same antiphon tune is managed in different tonal interpretations linked to regions. At last, one single example shows that even small melodic variants may emerge consequently in the use of individual dioceses or religious orders. The elements defined this way, identify, of course, the given centre not in their singularity but only in conjunction.