Almost since the birth of electronic music, composers have been fascinated by the prospect of integrating the human voice with its expressiveness and complexity into electronic musical works. This thesis addresses how performing with responsive technologies in mixed works, i.e. works that combine an acoustic sound source with a digital one, is experienced by participating singers, adopting an approach of seamlessness, of zero – or invisible – interface, between singer and computer technology. It demonstrates how the practice of composing and the practice of singing both are embodied activities, where the many-layered situation in all its complexity is of great importance for a deepened understanding. The overall perspective put forward in this thesis is that of music as a sounding body to resonate with, where the resonance, a process of embodying, of feeling and emotion, guides the decision-making. The core of the investigation is the lived experiences through the process of composing and performing three musical works. One result emerging from this process is the suggested method of calibration, according to which a bodily rooted attention forms a kind of joint attention towards the work in the making. Experiences from these three musical works arrive in the formulation of an over-arching framework entailing a view of musical composition as a process of construction – and embodied mental simulation – of situations, whose dynamics unfold to engage musicians and audience through shifting fields of affordances, based on a shared landscape of affordances.