This paper investigates hearers' use of response tokens (back-channels), in maintaining and differentiating their actions. Initial observations suggest that hearers produce a sequence of phonetically similar responses to disengage from the current topic, and dissimilar responses to engage with the current topic. This is studied systematically by combining detailed interactional and phonetic analysis in a collection of naturally-occurring talk in Norwegian. The interactional analysis forms the basis for labeling actions as maintained ("doing the same") and differentiated ("NOT doing the same"), which is then used as a basis for phonetic analysis. The phonetic analysis shows that certain phonetic characteristics, including pitch, loudness, voice quality and articulatory characteristics, are associated with "doing the same", as different from "NOT doing the same". Interactional analysis gives further evidence of how this differentiation is of systematic relevance in the negotiations of a next turn. This paper addresses phonetic variation and variability by focusing on the relationship between sequence and phonetics in the turn-by-turn development of meaning. This has important implications for linguistic/phonetic research, and for the study of back-channels. (Contains 4 figures, 4 tables and 2 notes.)