A catalogue of sounds from a laboratory population of Pigtailed macaques has been developed from spectograms. Sounds are divided into four general classes: clear, harsh and high-pitched calls, and miscellaneous sounds. It appears that all parameters of the vocal signal are independently manipulatable. A plot of selected spectral characteristics demonstrated the uniqueness of individual signals. In some instances, different sounds are developed by rearrangement of specific fragments, or by acoustical activities performed on similar sounds. This latter phenomenon, which will be termed mosaicism, parallels aspects of language design. Lastly, comparison of spectrograms for Pigtailed macaques with those published for Rhesus macaques (Macaca mulatta) reveals similarities in structure.