The app have several levels of difficulty. Each level has different frequency band characteristics. The user will hear sounds and it will be prompted to recognize which frequency is the correct answer. The method have been proved and it works. For years it was applied to students at our classes and each of them had an evolution during time, in which they really enhanced their recognizing of frequencies. This will always increase productivity as it will reduce the time mixing engineers use to modify parameters related with frequency on audio plug ins and equipment. The app also has the option of hearing pure tones, which is useful on the live sound daily work, to prevent and control undesired feedback.