Short answers, pulled from the story.
Nikolai Leonidovich Slonimskiy was born in Saint Petersburg during the final years of the Russian Empire. His family background included a grandfather named Rabbi Chaim Zelig Slonimsky who practiced Judaism.
The political landscape shifted violently with the 1917 Revolution forcing him to flee southward. He moved first to Kiev before heading to Constantinople and eventually settled in Paris where many other Russian musicians had already escaped.
In 1947 Slonimsky published Thesaurus of Scales and Melodic Patterns which became one of his most influential reference books. Frank Zappa relied heavily on the book for his own compositions while jazz musicians including Allan Holdsworth and Steve Rochinski studied its contents extensively.
Slonimsky assumed editorship of Baker's Biographical Dictionary of Musicians in 1958 and maintained this position until 1992 spanning nearly five decades of continuous service. The dictionary became a standard reference tool for researchers and musicians worldwide during his tenure.
After his wife Dorothy Adlow died in 1964 Slonimsky moved to Los Angeles. He taught at UCLA for three years before focusing on lectures and media appearances.