Early Infancy Studies emphasize the musical features of the early intersubjective mother-infant exchanges as primal and ubiquitous mark of human cognition. These studies have highlighted the domain of both sound pitch and time as key for defining such a musicality. Specifically concerning time domain, establishing regularities and small integer ratios patterns among sounds has been considered crucial. At this level, time relationships (ranging between 0.200 and 2 seconds) roughly define the structuralist notion of musical rhythm. However, studies on the expressive nature of musical infant-directed performances account that the relationship between such a structural time level and a lower time level (ranging 30 to 300 milliseconds), called microstructural, would be essential for defining, at least partially, the expressive content of the intersubjective encounter. Time at that microstructural level has been extensively studied in the field of music performance, through the generic concept of tempo rubato. These studies have focused on the relationships between microstructural and structural features as an explanation of the expressive content of musical performance. In this field, expression is defined as the set of systematic deviations of durational values from canonical (basic, normative) standards. Traditionally, this canonical dimension of the performance is represented by structural values as they can be expressed into notational terms (in a musical score). Concerning music performance we have proposed an evolutionary hypothesis for the so called "rubato’s expressive power" based on neurological, ontogenetic and phylogenetic evidence reinforcing the EI-TA link. Despite its significant progresses since music performance research has a clear cognitivist interest, it has mistreated microstructure as a trait of the performer’s personality. However, some studies foresee this search as a promising field for strengthening the EI-TA link. Advancing in this line requires that the notion of expression as emerging from tensions between structure and microstructure is musicological revisited. This paper proposes to revisit the notion of structure or "canonical dimension", which dialectically defines the microstructure or "expressive dimension" moving away from the ethnocentric anchoring of the classical studies in performance, namely music notation, and considering culture-dependent components compatible with oral musical cultures. From this point of view some possible implications for the study of intersubjectivity in early infancy are proposed and the "rubato’s expressive power" hypothesis is reformulated.