This paper reports on a workshop where participants produced physical mock-ups of musical interfaces directly after miming control of short electroacoustic music pieces. Our goal was understanding how people envision and materialize their own sound-producing gestures from spontaneous cognitive mappings. During the workshop, 50 participants from different creative backgrounds modeled more than 180 physical artifacts. Participants were filmed and interviewed for the later analysis of their different multimodal associations about music. Our initial hypothesis was that most of the physical mock-ups would be similar to the sound-producing objects that participants would identify in the musical pieces. Although the majority of artifacts clearly showed correlated design trajectories, our results indicate that a relevant number of participants intuitively decided to engineer alternative solutions emphasizing their personal design preferences. Therefore, in this paper we present and discuss the workshop format, its results and the possible applications for designing new musical interfaces.