Many music technologists have sought to reproduce the sonic signature of analog audio devices—amplifiers, compressors, signal processors, instruments—in the software domain. Assessing the effectiveness of the analog model involves a confusing mix of math, sound, electronics, appearances, and feelings, all of which are negotiated differently by users and designers. Drawing on ethnographic research at major software companies, along with close analysis of the technologies themselves, this chapter argues that “analog modeling” in the digital domain is one of the latest chapters in the long history of hearing tests, for it is in the moment of the listening test that engineers and users attempt to resolve competing epistemologies of sound. The listening test thus offers a privileged point of entry into both the classification and the experience of digital sound technologies.