The article is devoted to applications installed on a smartphone designed to master musical and theoretical disciplines, the principles and prospects for the use of them as they are not covered in the scientific literature. The work systematizes the most common programs, describes the algorithms of the applications EarToner, Tete, InPitch, EarPower, Earope, Auralia, Complete Ear Trainer, Absolute Pitch. The author formulates the principles of using electronic resources online in classes on the theory of music and solfeggio and reveals the potential of hearing development applications used by both teachers for classes with students and students at music universities and faculties themselves. The comparative analysis reveals the advantages and disadvantages of applications, evaluates the possibilities of their use by students as an electronic educational resource for solfeggio.