Hideo first learned piano and by the age of 14, he had enough musical training to conduct an amateur mandolin orchestra. At the comparatively late age of 16, he decided to learn cello. His father opposed a musical career, preferring his son to teach language or literature. When Saito entered Sophia University, he specialized in German but he continued to have an interest in music. Fortunately, one of his college friends was Prince Konoye, who was a professor and conducted a university orchestra. Konoye was also a member of the Imperial Family and it was quite impossible for his father to say no when Konoye went to Leipzig in 1923 and proposed to take young Hideo along for more musical studies.
It was not until he arrived in Leipzig that Saito realized how much higher German standards of music-making were than the level to which he was accustomed. So he stayed in Leipzig to continue his studies with Klengel at a time when fellow students with that master teacher included Feuermann and Piatigorsky. It may have been the typical Japanese reverence for a teacher that urged Saito to secretly memorize all of Klengel's fingerings of one of the Bach suites and then repeat them perfectly at a lesson. He was surprised when his master exclaimed, "Oh, no! Don't use MY fingering. There's a newcomer...called Casals....Much better to see what he does." Saito returned to Japan in 1927 and was appointed principal cellist of the New Symphony Orchestra, which was conducted by Konoye. He also appeared as soloist and formed the first chamber music organization in Japan. In 1930, he returned to Germany for more studies, this time with Feuermann, for two years. These studies were highly important and good for his development, but they were emotionally very difficult for a young Japanese student, for Feuermann expressed himself in a volatile and sarcastic manner that a Westerner might quickly have adjusted to, but which was hard for Saito to understand. One time, Feuermann said he would disown Saito as a pupil if he did not practice, so Saito practiced incessantly, even practicing mentally while riding a bus. He did return to Japan with a finely honed right-hand technique. When he got back, he resumed his position in the orchestra, which was not renamed the NHK Symphony Orchestra (NHK is the abbreviation for the country's broadcasting system). Joseph Rosenstock came from Germany to be the new conductor as Konoye had gravitated toward governmental and political matters. Saito learned conducting from him, particularly Rosenstock's clarity of beat.
The war years were as disastrous for Japanese concert activities as they were for all other aspects of life in that country. As the country picked itself up after the total defeat, Saito decided to become active in teaching music. He first opened a school for conducting and promoted chamber music societies. He gained the conviction that Western musical traditions could successfully be grafted on the strong Japanese respect for arts and culture. Saito became the leader in promoting Western music in Japan. The key, he thought, was to start with children. So in 1948, he founded a children's music school, starting with classrooms he rented from Tokyo Kasei Gakuen, a girls' finishing school. Intensive classes lasted all Saturday afternoon, for in Japan schools are open for half-days on Saturday. As his students advanced, he organized chamber music associations for them and then organized them into an orchestra.
He saw that the children had no place to go after they outgrew his school and therefore in 1952, he persuaded the Toho Gakuen to start a High School of Music for students aged 15 to 18. By Saito's plan, a few years later it added a Toho Gakuen College of Music. He took a personal part in every student's studies, so it is no exaggeration to say that he was a teacher to an entire generation of Japanese Western-style musicians. In 1964, he took the Toho Children's Orchestra on tour to America and later to the U.S.S.R. and Europe, all to amazed and wildly enthusiastic audience response. In 1974, he prepared the orchestra for another major tour, despite his declining health. He died just before its scheduled departure and his pupils decided that the greatest tribute to him would be to continue the orchestra's tour as scheduled. It was conducted on that tour by Saito's pupil Seiji Ozawa. He left behind him a flourishing tradition and there can be no doubt that the subsequent explosion of talented Japanese musicians on the world scene is a continuing tribute to Saito's memory.