Budzynski, T. H., & Stoyva, J. M. (1969). An instrument for producing deep muscle relaxation by means of analog information feedback. Journal of Applied Behavior Analysis, 2, 231-237.

An instrument that assists subjects in attaining deep muscle relaxation by means of analog information feedback is described. Subjects hear a tone with a pitch proportional to the electromyographic activity in a given muscle group. Results showed that subjects receiving this type of analog feedback reached deeper levels of muscle relaxation than those receiving either no feedback or irrelevant feedback. The basic method employed - electronic detection, immediate information feedback, and systematic shaping of responses - would seem potentially applicable to a variety of physiological events, and might be useful both in behavior therapy and in certain psychosomatic disorders.