[2] After his father's death in 1936, Sonoda continued his lessons; three years later he came under the tutelage of Leo Sirota, then resident in Japan.

In 1954 Herbert von Karajan made his Japanese debut conducting the NHK Symphony Orchestra with Sonoda as soloist.

Impressed by the young man's playing, Karajan persuaded Sonoda to study in Germany and wrote him a letter of recommendation.

Although admired for his performances of works by German classics such as Bach, Beethoven, and Brahms, Sonoda maintained a keen interest in modern music.

When the Shōwa Emperor died on January 7, 1989, NHK General TV followed their announcement of his passing by broadcasting Sonoda's recording of Chopin's Funeral March.