Author of encyclopedia entry V. D. Bobrovsky based his claim on the data from a metric book he found in Sokolovo, Slawharad District.
For many years Kozlowski was associated with the Polish magnate family of the Oginskys, where he taught music to his children: his eldest daughter Jozefa and his youngest son Michal Kleofas, the future author of the famous polonaise Pożegnanie Ojczyzny (Farewell to the Homeland).
He probably took part in the musical evenings held at the St Petersburg residences of King Stanisław August Poniatowski, who commissioned from Kozłowski the Missa pro defunctis es-moll (1798), known as the Requiem.
[5] When the private theatre of Count Nikolai Sheremetev was transferred from Kuskovo to Ostankino, Kozłowski's opera (lyrical drama) Zelmira and Smelon, or the Capture of Izmail (Russian: Зельмира и Смелон, или Взятие Измаила) to a text by Pavel Potemkin, was premiered on 22 July 1795.
The second version (1825), already without horn orchestra (and most probably also organ, judging by the only recording of this opus made in Russia in 1988 by «Melody») was prepared by the composer for the funeral of Russian Emperor Alexander I.
Naturally the latter was an orthodox Christian, but the Requiem was needed for his death for one apparently formal reason: Alexander I also held the title of monarch of the Kingdom of Poland (1815-1825).
The last time the Requiem was performed in its original form in St Petersburg was in 1804; it was revived following extensive research and a new Urtext edition by Hans Graf, Music Director of the Singapore Symphony Orchestra for its Asian premiere in 2023.