Purpose: One of the aims of expert knowledge management via information and communication technology is to improve the efficiency of knowledge transfer to non-specialists, and to facilitate the implementation of service-products that are adapted so as to be truly used. The aim of this paper is to describe an example in the domain of instrumental e-learning. Design/methodology/approach: Drawing on activity theory, this article describes a methodology that aims to guide the design process along the lines of the usage process. Findings: The co-design platform (CDP) allows the service designers and users to determine service-product definitions together, to facilitate the emergence of their uses. Research limitations/implications: Some of the experiments are still in progress as the development is iterative. Practical implications: To illustrate this method, the authors have designed and implemented an instrumental learning e-service for guitar music (e-guitare). Originality/value: The CDP gives a greater understanding of the transformation of the tool (proposals) into an instrument (proven demand), which is essential to the process of supplying the demand.