Guided by Damasio’s (2003) formulations on background emotions, this study examined the contour of infant affect during interactions with mother and father in relation to the emergence of symbolic expression. One hundred parents and infants were observed in face-to-face interactions and in play sessions at the toddler stage. Parent’s and infants’ affective states were coded in 1-s frames, and synchrony was assessed. Toddlers’ play was microcoded for symbolic level and for reciprocity and intrusiveness. Infant affective contour with mother was rhythmic with 1 episode of positive arousal framed by social gaze. Affective contour with father contained several peaks of positive arousal of shorter duration. Symbolic complexity was comparable and preserved the parent-specific contours, with quicker latencies, higher frequencies, and shorter durations of complex symbolic episodes with father. Sequential relations emerged between parent’s and child’s symbolic expression, and maternal reciprocity and intrusiveness were sequentially linked to symbolic expansion or constriction, respectively. Parent-infant synchrony and the parent’s support of toddler symbolic play predicted symbolic complexity. The need to include time in research on emotions and the dyadic origins of positive emotions are discussed.