This paper has a dual aim: to situate functionalities among the complex of factors that help shape online interactions and to explore the heterogeneity of audio conferencing and its implications. Following a critical discursive synthesis of the treatment of variables in the literature, attention focuses on the distinctive and diverse characteristics of synchronous audio environments. The existence of a synchronous-asynchronous dichotomy is questioned and the effects of a number of differences are highlighted. As a further illustration, the paper next undertakes a comparison of "Lyceum" and "Wimba Voice Direct." The main features of the two environments are introduced and a detailed analysis of their text and voice chat facilities is carried out. In the last section the benefits of text-based CMC are revisited through the lens of voice chat technology. It is concluded that the benefits of CMC appear to have been overstated and that no general claims can be made about voice CMC, but that collectively, well documented studies could provide a useful source of information on the level of contingency of particular findings.