In 1782 he went to Bologna to study with Padre Martini and Stanislao Mattei; three years later he was accepted into the Accademia filarmonica. Returning to St. Petersburg in 1785, he taught at the theatrical school and composed operas. From 1797 he was répétiteur for the imperial theater under Paul I. He composed about 30 operas including Yamshchiki na podstave [The Coachmen at the Relay Station] (1787); Vecherinki [Soirées] (1788); Orfey i Evridika (1792), Amerikantsy [The Americans] (a comic opera) (1800), and Zolotoye yabloko [The Golden Apple] (performed after the composers death in 1803). The most successful for decades was his opera-melodrama Orfey i Evridika to a text by Yakov Knyazhnin. It was re-staged in Soviet times in 1947 in Moscow, and in 1953 and in 1961 in Leningrad.
The famous one-act opera Anyuta to a text by Mikhail Popov has been occasionally attributed to Fomin (which is not a certainty).  In addition, Fomin has been credited with the music of another successful Russian opera Melnik – koldun, obmanshchik i svat (The Miller who was a Wizard, a Cheat and a Match-maker, Moscow, 1779), on a subject resembling Rousseau’s Le devin du village: it is possible that this was his revision of the music compiled by a theatre violin player, Mikhail Sokolovsky.