When hearing a voice for the first time, the percept does not fall into a vacuum. The present work aimed at understanding the structure, timing and acoustical bases of voice first impression formation (VFI), as well as the influence of contextual and motivational settings on this mechanism. First, we report a bi-dimensional structure to VFI formation, with dimensions of valence-trustworthiness and dominance majorly leading the impression. Second, we report dimension-related timings, with faster impression of dominance than valence. Thirdly, we report different effects of context (recruitment scenario) relative to the dimension of evaluation as well as speaker's sex. Acoustical analyses throughout all studies suggest that a dynamic interaction between features underlies these processes. Results are integrated together into a model of VFI and discussed in light of their significance for future research and application for speech synthesis.