He was a child prodigy on the piano, and made his New York City debut in 1911, with a concert at the Metropolitan Opera House.

He then studied piano in Berlin, Germany with Ferruccio Busoni and others, making his debut in New York City in a joint concert with Eugène Ysaÿe in 1916.

After the U.S. entry into World War II, Rubinstein (then 43) enlisted in the U.S. Army with the rank of captain in the Fifth Service Command.

From 1942 to 1944 he traveled 20,000 miles and participated in seventy-five concerts for servicemen in North Africa, Sicily, and Italy.

After the war Rubinstein returned to Cleveland to resume the directorship of CIM, which expanded greatly over the next decade.