MuCap (muCap) is a software package (citeware) for economic experiments enabling experimenters to analyze emotional states of subjects using z-Tree and FaceReaderTM. muCap is able to create videos of subjects on client computers based on stimuli shown on screen and restrict recording material to relevant time frames. Another feature of muCap is the creation of time stamps in csv format at prespecified screens (or at prespecified points in time) during the experiment, measured on the client computer. The software makes it possible to import these markers into FaceReaderTM easily. Until recently, connecting z-Tree and FaceReaderTM was only possible using workarounds or by undertaking many successive actions manually. muCap is the first program that significantly simplifies this process with the additional benefit of extremely high precision. This paper describes the usage, underlying principles as well as advantages and limitations of muCap. Furthermore, we give a brief outlook of how muCap can be beneficial in other contexts.