Description: This paper focuses on how a chorister/soloist, playing the dog " Lapak " in Leos Janacek's The Cunning Little Vixen at the Geneva opera house, prepares for her part in the lyrical piece. The observations show that learning a part is more than " simply applying " the producer's and composer's instructions, but rather consists in a situated construction. Although the staging of the opera is planned in advances, rehearsals of the play show that the chorister is continually adjusting her action to the situation and looking for the stabilization of a form. Learning a part is thus a dynamic activity (Grossetti, 2004). It does not result from an essentialist process of planning and prescription (Durand & Veyrunes, 2005), but rather from a process of successively enacted transformations. Interested in probing further the field of artistic activity, we consider in this paper how the dynamics of creativity can be approach from the standpoint of metaphor theory (Lakoff and Johnson, 1980). In our view, the transformation of the chorister/soloist action proceed from a double metaphorical engagement. On the one hand, the chorister mobilizes metaphoric arguments to explain how she learns a role. On the other, metaphors are also the very stuff of the way she acts, they are in the manner in which she thinks and plays her part as Lapak. More generally, metaphors guide the actions of the actors playing a part in the set up of an Opera. On this basis, we propose that 1) the activity of creating results from a process including a metaphorical transfer of significations, and 2) thoughts and actions' transformations proceed at least in part from the uses of metaphors in rehearsals. Methodology: The data analysed for the paper comes from a corpus constructed in the course of six months of ethnographic fieldwork and interviews documenting different dimension of the set up of an opera. The data discussed here consists in " self-confrontation interviews " (conducted in accordance with principles set out in French " situated activity theory ") during which the chorister/soloist is asked to comment on video recordings of the rehearsals of Act 1 of The Cunning Little Vixen. Data analysis includes 1) identifying metaphors used in the corpus, and 2) identifying metaphors'influence on the chorister's thoughts and actions in learning how to play her lyrical part. Conclusions: The results show 1) how the chorister engages metaphors in her activity, 2) how the metaphors reflect her perception of The Cunning Little Vixen's story and the producer's and composer's instructions, 3) how she establishes her manner of thinking and doing the dog Lapak. Through this, the paper shows the function of metaphors in the transformation of knowledge and action.