He graduated in sacred music at the State University of Music in Detmold An exam. Special studies of French organ music followed with Marcel Lanquetuit, organist of Rouen Cathedral. After his first activities as organist at the Ev.Inselkirche on Juist (1969-1973) and in the old town Nicolaikirche in Bielefeld (1973-1979) Hielscher was appointed organist at the Ev.Marktkirche in Wiesbaden1979 and from 1987 to 2004 he was organist at the concert hall organ in the Kurhaus Wiesbaden. His numerous tours have taken him to almost all European countries, including the USA, with more than 3,800 solo concerts (72 US tours so far) and several times to Canada, Australia, New Zealand, Japan, Hong Kong, Singapore , Bangkok and South Africa. Many of his radio and television recordings, as well as most of the 22 CDs recorded to date, are devoted to French organ music of the late Romantic period, Anglo-American music and transcriptions of orchestral works. His organ compositions and books have been published by German, English and American publishers. In 1985 Hielscher was named "Chevalier de l'Ordre des Arts et des Lettres" by the French Minister of Education in Paris for his worldwide services to French organ music. In 2009 he was awarded the "Citizens' Medal of the capital Wiesbaden in silver". In 2019, the Hessian Ministry of Science and Art in Wiesbaden awarded him the "Certificate of Honor for Art and Culture of the State of Hesse".