"Selig sind die Toten" was a compostion of Jahn's that possibly gives the earliest indication of his work and life. It was written in and is now stored in Strasbourg. In 1643 he was a student at Konigsberg having written his "Musicalische Jubel-Frewde" in 1644 for a celebration there. He was persecuted in Germany for his religious beliefs and took residence in Upper Silesia. By 1654 he had settled in Sagan, Silesia as Protestant worship was still allowed to take place. He acted as the headmaster of a school there until he received his own parish in Eckersdorf (1663). Jahn's "Musicalische" was set for up to six choirs after the Italian style. He composed as many as two hundred and fifty songs, songs by Luther, sacred songs, a funeral motet and the cantata "Selig sind. . ." The fifty sacred songs were confined to the passion story.