This paper describes a method of corrective phonetics based on perceptual phonetics, because it is in this area that contact with a foreign language is first established. Methods of correcting phonetic perception by frequency manipulation (using the frequency selector "SUVAG-Lingua") within the framework of the verbo-tonal method of foreign language teaching are discussed, and it is argued that further investigation will be necessary before conclusive judgements as to the didactic and linguistic value of the frequency selector can be made. This paper is a short introduction to the stage of development of this technical aid in language teaching and aims also to stimulate further investigation, because no relevant research or experimentation has been carried out in the United States, although frequency selectors have been in use in several European countries for a considerable amount of time. (Author)