Complex sentence: Philip Hart was for many years organist of churches in London: he became assistant organist of St Andrew Undershaft in 1696, sole organist from 1697 until his death; he was organist of St Michael, Cornhill from 1704 to 1723.
Split into simpler sentences: Philip Hart was for many years organist of churches in London. He was organist of St Michael, Cornhill from 1704 to 1723.