he then served as organist at the prominent riverside church in new york city, from 1946 to 1965. the organ was built for him by famed organ builder g. donald harrison, master builder of the mormon tabernacle organ plus others. under his direction, the riverside organ was expanded to become one of the largest in north america. his extemporaneous hymn accompaniments at riverside's sunday services and concert performances were widely acclaimed, and fans would wait after church services for hours to meet him. recordings made during this period brought his playing to larger audiences. among his recordings, some of which are now overlooked, the transcriptions he improvised upon: "songs at sunset, vale of dreams, silhouettes". in 1965, fox retired from the church to devote himself to performing full-time.