This work aims to give a feeling of the roles that discipline-oriented subject classifications play in scientific communication, in the perspective of the Open Archives movement for the free dissemination of information in research activities. Mathematics, and Mathematics Subject Classification, will be the focuses around which we will move to discover a variety of presentation modes, protocols and tools for human and machine interoperability. The Open Archives Initiative (OAI) is intended to be the effective framework for this play, which is presented to you by two university librarians at Padova and a researcher at Milano, Italy. The present work is divided into two parts. In the first one, we start by giving some examples of the most important subject classification schemes in mathematics and related disciplines. Then we sketch the structure of subject classification schemes in view of browsing. Finally we give an idea of different browsing modalities, which are demonstrated by the tools we produced and collected in The Scientific Classifications Page. In the second part, we give an account of different strategies for e-print communication in scientific research, up to the basic definitions of the Open Archives Initiative. A review of the functionalities actually implemented in OAI compatible archives managed by the EPrints software will lead us to some working hypothesis about the roles that subject classifications in mathematics and related disciplines can play in the scenarios of the Open Archives movement.