John R. Bartosh was born on June 6, 1924. His father, John Sr., emigrated from Czechoslovakia. His father served in the Army in World War I and was wounded in Alsace Lorraine. John, Jr. had two sibilings.
John attended Tredyffrin/Easttown high school. John was an accomplished violinist. During his senior year, the Philadelphia Orchestra held auditions for talented high school musicians to accompany them in a production of Gilbert and Sullivan's HMS Pinafore. John was one of the few students chosen to accompany them at the Academy of Music.
John graduated in 1942. He pursued his talent, but also worked as a crane operator to pay the bills.