This paper presents a cooperative intelligent tutoring system which adopts a multiagent approach, here applied to Musical Harmony domain. This system integrates an ITS with a Web hypermedia component resulting in a Web-based distance educational system. The essential idea in our research is to define and develop an environment that provides effective means to involve human learners, tutoring system and human teachers, in productive cooperative interactions based on problem solving situations. The system architecture consists of eight main entities: Learner, Teacher, Human Expert System, Set of artificial tutoring agents, Hypermedia Component, as well as, three interfaces modules to assure interactions between theses entities. Here we give an overview of the system, emphasising the multi-agent system and the main interactions between human and artificial agents. We also bring out particular aspects related to domain knowledge modelling and its consequences in the multiagent design, learner modelling, and a mechanism from the tutoring system to supporting adaptive navigation on the teaching material.