sixtus was chancellor of the prince-bishop john iv tulbeck of freising, who resigned in 1473 in favor of tannberg. tannberg resigned as bishop of gurk, leaving the post to lawrence of freiberg. between 1481 and 1483, during tannberg's reign, a vault was designed, which still exists today, for the nave of the freising cathedral. tannberg was very pious and led to several diocesan synods and introduced profound reforms of the clergy in his diocese. he also founded in 1484 his own cathedral choir, who would contribute to more worthy church services. he died on 14 july 1495 in the monastery of the canons regular of st. augustine in frankenthal, near worms. he was buried in the freising cathedral.