he article gives a phonetic commentary on the grammar manuals of A.Kh. Vostokov (1781–1864), compiled by a scientist in 1831. Linguistic evidence of the realizations of the mutabil phoneme <г>, phoneme <ш’:>, which in the 19th century was still an affricate, and the pronunciation of the letter ѣ. The functions of the letters Ъ, Ь and Й are revealed: in the system of A.Kh. Vostokov they denote the sound [j], participate in the hardening and softening of previous consonants and alternations with vowels. The general approach of the researcher to the sound side of the Russian language is analyzed, for which we have attracted other works by Vostokov, where phonetic questions were raised. The influence of orthography on the perception of language is also considered: it had a decisive influence on the description of phonetics in the 19^th century.