Short answers, pulled from the story.
Nicolas Slonimsky was a Russian-American musicologist, conductor, pianist, lexicographer, and composer born in Saint Petersburg and died on the 25th of December 1995 in Los Angeles at age 101. He is best known for writing the Thesaurus of Scales and Melodic Patterns, the Lexicon of Musical Invective, and for editing Baker's Biographical Dictionary of Musicians.
The Thesaurus of Scales and Melodic Patterns is a reference book Slonimsky published in 1947 that became a sourcebook for composers and performers. It influenced jazz musicians and composers including John Coltrane, Frank Zappa, Allan Holdsworth, Paul Grabowsky, and Steve Rochinski, and remained in print 60 years after publication.
Slonimsky conducted the world premiere of Charles Ives' Three Places in New England in 1931 at New York's Town Hall, and the world premiere of Edgard Varese's Ionisation for thirteen percussionists in 1933. He also led concerts in Havana, Paris, Berlin, and Budapest featuring works by Ives, Ruggles, Cowell, Amadeo Roldan, and Alejandro Garcia Caturla.
The Lexicon of Musical Invective, published in 1953, is a collection of scathing contemporary critical reviews of major composers subtitled "Critical Assaults on Composers since Beethoven's Time." It documents how severely critics misjudged composers who are now considered great figures in the canon.
Slonimsky became editor of Baker's Biographical Dictionary of Musicians in 1958 and remained its head editor until 1992. He developed a reputation for factual accuracy across those decades of editing.
Slonimsky became a personal friend of avant-garde composer and rock guitarist Frank Zappa. In 1981 he performed some of his own compositions at a Zappa concert in Santa Monica, California. He named his cat Grody-to-the-Max after learning the phrase from Zappa's daughter Moon Zappa.