We have analysed the basic characteristics of music playback at sight-reading of three two-line classic music selections of varying textures and complexity: a two-voice polyphonic musical piece, a theme and a variation of homophonic-harmonic musical piece. These characteristics serve as objective indicators of the musicians' skill of sight-reading, and the complexity of musical selection. Applying an original technique of eye movement recording without fixating the head, we studied the eye-hand span i.e. the time from reading the text to music playback. Our findings reveal, that the eye-hand span depends on the texture of the performed musical piece and inversely correlates with the number of errors as well as directly correlates with the rate of stability in the performance. This parameter may serve as an objective measure of the sight-reading ability. It is connected with the complexity of a musical piece and, presumably, characterizes the working memory capacity of musicians.