The characteristics of compact cassettes of different types produced both in the CIS countries and in Japan, USA, Western Europe, Southeast Asia are given. The effect of each measured characteristic on sound quality is described in detail. For each type of cassette, the parameters of the optimal recording mode are indicated, knowing which, you can adjust the tape recorder to obtain the highest possible quality. The book belongs to the era of the dawn of cassette recorders and is of interest to those who are still engaged in them.