In 1731, the Hellendaal family moved to Utrecht where Pieter - still juvenile - became organist for the St. Nicholas church, (Nicolaïkerk :nl:Nicolaïkerk (Utrecht), a highly visible and prestigious position: Popularly known as the "Santa Claus" Church, St. Nicholas was the second oldest parish church in the Netherlands and had been recognized for many centuries as a leader for organ music. In 1120 it was already well known as the first Dutch church to use a portable organ. The main organ in the 1730s had been built by Peter Gerritsz during the years 1477-1479, and is the first large Dutch organ and was famous as one of the first and best preserved anywhere from the Middle Ages. Under Johannes' supervision, son Pieter at age ten played the Gerritsz organ. From January 1732 (when Pieter was about twelve) until 1737 he was appointed an organist. In that year, when Pieter was 15, the Hellendaal family moved, this time to Amsterdam.