Main purpose of this chapter is to show and describe in detail how P. F. Lazarsfeld contributed to the development of research methods and techniques within the field of media studies. The awareness is focused especially on Program Analyzer, the special device that P. F. Lazarsfeld invented and used together with F. Stanton for researching audience reactions during exposure to the radio program. Apart from description of the machine itself, the attention is paid to unique type of research findings that Program Analyzer has been bringing and to the research design that P. F. Lazarsfeld used in order to maximize the validity and relevancy of results coming from this type of audience reactions study. In this chapter, we try to show the impact of Lazarsfeld’s innovations on media research techniques and we point out how the proposed research design influenced other studies aiming to help with improvement of radio programs. Finally, we underline some of the key elements of Lazarsfelds’ legacy.