This man compiled a book of "critical assaults on composers since Beethoven's time" in his book A Lexicon of Musical Invective. For 10 points each:
[10h] Name this Russian-American conductor, composer and writer. Virgil Thomson was among the many composers who drew heavily on this man's Thesaurus of Scales and Melodic Patterns.
ANSWER: Nicolas Slonimsky [or Nikolai Leonidovich Slonimsky]
[10m] This French composer, who had been best man at Slonimsky's wedding, got Slonimsky to conduct the premiere of his percussion work Ionisation. This so-called "father of electronic music" also wrote Deserts and Density 21.5.
ANSWER: Edgard (Victor Achille Charles) Varèse
[10e] The 1995 piece Slonimsky's Earbox was written by this composer to reflect his reliance on Slonimsky's Thesaurus. This American composer wrote the operas The Death of Klinghoffer and Nixon in China.
ANSWER: John Coolidge Adams