Complex sentence: Vvedensky's paternal grandfather was Jewish but converted to Christianity and served as a psalmist (cantor) in the diocese of Novgorod the Great and in the process of converting changed his surname to Vvedenskii after Vvedenia, the feast of the Presentation of the Virgin.
Split into simpler sentences: Vvedensky's paternal grandfather was Jewish but converted to Christianity and served as a psalmist (cantor) in the diocese of Novgorod the Great. In the process of converting his grandfather changed his surname to Vvedenskii after Vvedenia, the feast of the Presentation of the Virgin.