The aim of this article is to analyse the theme of evaluation of performances in the performing arts sector through the structure of customer- supplier relations, which constitute the warp on which is woven the weft of organisational activity. Thus, attention will be focused on the case of opera houses. Here, the theme of evaluation will be adopted as the criterion for planning and organising business processes. On the basis of this approach, the structure of the production process of an opera will be reconstructed. Subsequently the four phases of the customer/supplier transaction by which the performance can be evaluated will be analysed. In the final paragraph, the role of artistic management as alleviator or provider of knowledge to the «founding parties» will be hihlited.