1959 – 1964
Conservatory in Košice (violin), later consultations with Prof. Mária Hlouňová, Prague
1964 – 1967
deputy concert master in Košice Radio Orchestra, later in the Orchestra of Jozef Gregor Tajovský Theatre in Banská Bystrica
1967 – 1969
concert master in Košice Radio Orchestra
1969 - 2011
concert master of the State Philharmonic Košice (in this position he worked 42 years)
1976 – 2007
conductor and artistic director of Košice Teachers' Choir
conductor of academic choir Collegium Technicum in Košice
cooperation with Church Choir of St. Cecilia in St. Elisabeth Cathedral in Košice
With the philharmonic orchestra Karol Petróczi attended many different tours and regularly performed as its soloist. In chamber music he for a long time cooperated with pianist Anna Ličková. As concert master he has worked also abroad – Cairo Symphony (Egypt), Camerata Helvetica, and Orquesta Symfonica de Asturias (Spain).
Significant is his work is the field of choir conducting. He was the longtime choirmaster of Košice Teachers' Choir (cooperation lasts to the present) and choir Collegium Technicum, which under his leadership has received important awards and recognition at international competitions and festivals.
He is a respected pedagogue at the Conservatory in Košice and his significant educational achievements rank him among the top Slovak violin professors. He also taught at Tokyo University in Japan.