At the same time, ongoing studies of vocal communication in wild primate populations continue to reveal new insights into the social and environmental contexts of many primate calls, and the range of known primate vocalizations has increased dramatically with the development of more sophisticated and accessible auditory equipment and software that enables the recording and analysis of higher-fidelity and broader-band recordings, including documenting very high frequency (i.e. ultrasound) vocalizations. 

Historically the relative importance of primate calls has been evaluated qualitatively by the perception of the researcher, but new methods and approaches now enable a greater appreciation for how signals are used and perceived by the primates in question. The integration of anatomical and behavioral data on acoustic communication and the environmental correlates thereof has significant potential for reconstructing behavior in the fossil record. This confluence of factors and accumulating evidence for the sophistication and complexity in both the signal and its interpretation indicate that a book synthesizing this information across primates is warranted and represents an important contribution to the literature.