The potential of the diversity of specific timbre inclusions in the music of the 20 th and 21 st centuries is used quite differently: this factor determines a special place of work forms for the development of timbral hearing at sol-fa lessons, namely, that of the auditory analysis. In this research, the authors have developed diagnostic music assignments for identifying the level of future professional musicians' timbral hearing on the basis of the auditory analysis. During case study authors elaborated and piloted levels, indicators of development and diagnostic assignments for identifying the level of timbral hearing on the basis of different types of auditory analysis during the sol-fa lessons in a secondary music school.