Bruno Bjelinski (born Bruno Weiss; 1 November 1909 – 3 September 1992) was one of a most influential Croatian composers in the 20th century.
 He was extremely prolific as a composer.
 His unique musical style was built upon the music of Poulenc, Hindemith, Ravel and Milhaud.
 He developed his own and recognizable musical language with the elements of neoclassicism.
 Bjelinski composed six operas, three ballets, 15 symphonies, 2 cello concertos, a cantata, piano music, songs, chamber music, and concertos for piano, violin, viola, bassoon, flute, and piano duo.
 He also composed music for the Croatian football movie "Plavi 9".
Ecology is a new science and considered as an important branch of biological science, having only become prominent during the second half of the 20th century.
 Ecological thought is derivative of established currents in philosophy, particularly from ethics and politics.
 Its history stems all the way back to the 4th century.
 One of the first ecologists whose writings survive may have been Aristotle or perhaps his student, Theophrastus, both of whom had interest in many species of animals and plants.
 Theophrastus described interrelationships between animals and their environment as early as the 4th century BC.
 Ecology developed substantially in the 18th and 19th century.
 It began with Carl Linnaeus and his work with the economy of nature.
 Soon after came Alexander von Humboldt and his work with botanical geography.
 Alfred Russel Wallace and Karl Möbius then contributed with the notion of biocoenosis.
 Eugenius Warming’s work with ecological plant geography led to the founding of ecology as a discipline.
 Charles Darwin’s work also contributed to the science of ecology, and Darwin is often attributed with progressing the discipline more than anyone else in its young history.
 Ecological thought expanded even more in the early 20th century.
 Major contributions included: Eduard Suess’ and Vladimir Vernadsky’s work with the biosphere, Arthur Tansley’s ecosystem, Charles Elton's "Animal Ecology", and Henry Cowles ecological succession.
 Ecology influenced the social sciences and humanities.
 Human ecology began in the early 20th century and it recognized humans as an ecological factor.
 Later James Lovelock advanced views on earth as a macro-organism with the Gaia hypothesis.
 Conservation stemmed from the science of ecology.
 Important figures and movements include Shelford and the ESA, National Environmental Policy act, George Perkins Marsh, Theodore Roosevelt, Stephen A. Forbes, and post-Dust Bowl conservation.
 Later in the 20th century world governments collaborated on man’s effects on the biosphere and Earth’s environment.
Twelve-tone technique—also known as dodecaphony, twelve-tone serialism, and (in British usage) twelve-note composition—is a method of musical composition devised by Austrian composer Arnold Schoenberg (1874–1951) and associated with the "Second Viennese School" composers, who were the primary users of the technique in the first decades of its existence.
 The technique is a means of ensuring that all 12 notes of the chromatic scale are sounded as often as one another in a piece of music while preventing the emphasis of any one note through the use of tone rows, orderings of the 12 pitch classes.
 All 12 notes are thus given more or less equal importance, and the music avoids being in a key.
 Over time, the technique increased greatly in popularity and eventually became widely influential on 20th century composers.
 Many important composers who had originally not subscribed to or even actively opposed the technique, such as Aaron Copland and Igor Stravinsky, eventually adopted it in their music.
Dieterich Buxtehude (] ; Danish: "Diderich" , ] ; c. 1637/39 – 9 May 1707) was a Danish-German organist and composer of the Baroque period.
 His organ works represent a central part of the standard organ repertoire and are frequently performed at recitals and in church services.
 He composed in a wide variety of vocal and instrumental idioms, and his style strongly influenced many composers, including Johann Sebastian Bach.
 Today, Buxtehude is considered one of the most important composers in Germany of the mid-Baroque.
Béla Viktor János Bartók ( ; ] ; 25 March 1881 – 26 September 1945) was a Hungarian composer, pianist and an ethnomusicologist.
 He is considered one of the most important composers of the 20th century; he and Liszt are regarded as Hungary's greatest composers .
 Through his collection and analytical study of folk music, he was one of the founders of comparative musicology, which later became ethnomusicology.
A violin concerto is a concerto for solo violin (occasionally, two or more violins) and instrumental ensemble, customarily orchestra.
 Such works have been written since the Baroque period, when the solo concerto form was first developed, up through the present day.
 Many major composers have contributed to the violin concerto repertoire, with the best known works including those by Bach, Bartók, Walton, Beethoven, Brahms, Bruch, Mendelssohn, Mozart, Paganini, Prokofiev, Shostakovich, Sibelius, Tchaikovsky, and Vivaldi.
Veljo Tormis (7 August 1930 – 21 January 2017) was an Estonian composer, regarded as one of the greatest living choral composers and one of the most important composers of the 20th century in Estonia.
 Internationally, his fame arises chiefly from his extensive body of choral music, which exceeds 500 individual choral songs, most of it a cappella.
 The great majority of these pieces are based on traditional ancient Estonian folksongs ("regilaulud"), either textually, melodically, or merely stylistically.
Heinrich Schütz (] ; 18 October [O.S. 8 October] 1585 – 6 November 1672) was a German composer and organist, generally regarded as the most important German composer before Johann Sebastian Bach and often considered to be one of the most important composers of the 17th century.
 He wrote what is traditionally considered to be the first German opera, "Dafne", performed at Torgau in 1627, the music of which has since been lost.
The city of Paris has been an important center for European music since the Middle Ages.
 It was noted for its choral music in the 12th century, for its role in the development of ballet during the Renaissance, in the 19th century it became famous for its music halls and cabarets, and in the 20th century for the first performances of the Ballets Russes, its jazz clubs, and its part in the development of serial music.
 Paris has been home to many important composers, to name a few: Jean-Baptiste Lully, Jean-Philippe Rameau, Christoph Willibald Gluck, Niccolò Piccinni, Frédéric Chopin, Franz Liszt, Jacques Offenbach, Georges Bizet, Claude Debussy, Maurice Ravel, Hector Berlioz, Paul Dukas, Gabriel Fauré, César Franck, Charles Gounod, Jules Massenet, Vincent d'Indy, Camille Saint-Saëns, Erik Satie, Igor Stravinsky, Sidney Bechet...
Sergei Sergeyevich Prokofiev ( ; Russian: Сергей Сергеевич Прокофьев , "Sergej Sergejevič Prokofjev" ; 27 April 1891 – 5 March 1953) was a Soviet composer, pianist and conductor.
 As the creator of acknowledged masterpieces across numerous musical genres, he is regarded as one of the major composers of the 20th century.
 His works include such widely heard works as the March from "The Love for Three Oranges," the suite "Lieutenant Kijé", the ballet "Romeo and Juliet" – from which "Dance of the Knights" is taken – and "Peter and the Wolf."
 Of the established forms and genres in which he worked, he created – excluding juvenilia – seven completed operas, seven symphonies, eight ballets, five piano concertos, two violin concertos, a cello concerto, a Symphony-Concerto for cello and orchestra, and nine completed piano sonatas.

Question: What major composer of Violin concertos is considered one of the most important composers of the 20th century?
Answer: Béla Viktor János Bartók