Subsequently, he enrolled at the University of Fribourg law school, and he finished his doctorate in 1904.  He also completed graduate studies in political science, and finance in Leipzig, Munich, Berlin  and Vienna.   German science passed as unequal models at the beginning of the twentieth century. 

When he was thirty years old, he opened a law office in Bulle (Switzerland), after having worked for two years as the attorney general in Fribourg.  At the same time, he became the director of the Crédit Gruyérien in Bulle.  In 1906 he married Miss Julietta Meyer, the daughter of the Count Jules de MEYER  and Maria POCOBELLI Meyer.   Jean-Marie and Juliette Musy had seven children: Pierre, Marie-Christine,  Benoît,  Vérène, Luigi, Marie-Thérèse, and Christophe.  Jean-Marie's sister, Pauline Musy, married Charles Comte in 1908 and five children were born.

In 1913, Jean-Marie and Auguste Barrans, seeing that the Gruyère cheese commerce is disorganized, take the initiative to help the cheese producers of the region.  The two men from Gruyère discard the concepts of a central cheese cooperative with the goal to take "the cheese on consignment, for the accounts of its producers, and to obtain better sale prices. (http://www.gruyere.com/histoire.htm 1997)."

In 1914 he was elected to the National Council in Bern.  He rapidly became one of the most competent representative from the French region (Romande) of Switzerland to the National Assembly in Bern.  In 1919, at the age of only 43 years old, he was elected Federal Councillor and devoted all of his strength to the arduous task as the head of the Finance and Customs Department.  Jean-Marie Musy was Vice-President in 1924 and elected President of Switzerland (Swiss Confederation) in 1925 and 1930.

From 1936-1939 several important Swiss financial organizations, in addition to foreign governments sought his valuable economic recommendations.  After many years of service to his country  he permanently  retired  in 1939 and lived in the Castle of Middes (canton of Fribourg - Switzerland) with his family.