The development of the cushion-like musical interface called the sponge started about seven years ago. Since then, it was extensively used to perform in various settings. The sponge itself is described, but the main focus is on the evolution of the mapping strategies that are used. The author reviews the guidelines proposed by other researchers and explains how they were concretely applied with the sponge. He concludes that no single strategy constitutes a solution to the issue of mapping and that musical compositions are complex entities that require the use of a multitude of mapping strategies in parallel. It is hoped that the mappings described combined with new strategies will eventually lead to the emergence of a musical language that is idiomatic to the sponge.