Question: Why is the ethnomusicologist, Bela Viktor Janos Bartok's Piano Concerto No. 2 in G major considered notorious?
Context: In G Major is a ballet made for New York City Ballet's Ravel Festival by ballet master Jerome Robbins to the composer's "Piano Concerto in G Major" (1928–31).  The premiere took place May 15, 1975 at the New York State Theater, Lincoln Center, with lighting by Mark Stanley.  The Paris Opera Ballet commissioned scenery and costumes by Erté when it staged Robbins' ballet under the name "En Sol", decor which has subsequently been borrowed by City Ballet.  Ravel composed the concerto after travelling in the United States and is reported to have described the work as "... written in very much the same spirit as those of Mozart and Saint-Saëns," and said that "it uses certain effects borrowed from jazz, but only in moderation." The Piano Concerto No. 2 in D minor, Op. 40, was written in 1837 by Felix Mendelssohn and premiered at the Birmingham Festival of 1837, an event that also saw the premier of Mendelssohn's St. Paul Oratorio.  He had already written a piano concerto in A minor with string accompaniment (1822), two concertos with two pianos (1823 – 4), and his first Piano Concerto.  The concerto is about 23 minutes in length, and is scored for strings, flute, clarinet, oboe, horn, trumpet, and timpani. Béla Bartók's Piano Concerto No. 2 in G major, Sz.  95, BB 101 (1930–31) is the second of three piano concerti, and is notorious for being one of the most difficult pieces in the repertoire. The Yellow River Piano Concerto () is a piano concerto arranged by a collaboration between musicians including Yin Chengzong and Chu Wanghua, and based on the "Yellow River Cantata" by composer Xian Xinghai.  Since its politicised premiere in 1969 during the Cultural Revolution, the Concerto has become popular in China and amongst overseas Chinese nationalists.  It is noted for a difficult solo part.  This piano concerto and the Butterfly Lovers' Violin Concerto, which tells the story of the Butterfly Lovers, are two internationally known Chinese works that combine Western music methodology with Chinese source materials. The last complete piano concerto by Sergei Prokofiev, Piano Concerto No. 5 in G major, Op. 55, dates from 1932. The compositions of Sergei Rachmaninoff (1873–1943) cover a variety of musical forms and genres.  Born in Russia, he studied at the Moscow Conservatory with Nikolai Zverev and Anton Arensky, and while there, composed some of his most famous works, including the first piano concerto (Op. 1) and the Prelude in C-sharp minor (Op. 3, No. 2).  Although spread over three different opuses, he did go on to complete an important set of 24 preludes in all the major and minor keys.  His Symphony No. 1 (Op. 13) was one of his first compositions as a "Free Artist" after graduation, and subsequently his first critical failure.  The derision he received sent him into depression.  After being sent through autosuggestive therapy, he composed his second piano concerto (Op. 18), which is still part of the major orchestra repertoire today.  In 1909, he made his first tour of the United States, and composed Piano Concerto No. 3 (Op. 30), notable for its difficult cadenza.  After this, due to migration from Russia in 1917 and his busy concert career, his output as a composer decreased, and during this period, he completed only six compositions.  His last work, "Symphonic Dances" (Op. 45), was completed in 1940. Mariela Cingo (born 14 February 1978 in Korçë, Albania) is an Albanian pianist currently residing in the United Kingdom.  She started to learn music from the age of 6, and gave her first concert at the age of 7.  By the time she was 12, she had played the Haydn Piano Concerto in D with the Korcë Philharmonic Orchestra.  At the age of 17 she moved to the UK to continue her studies under the tuition of Professor Raphael Terroni at the London College of Music.  There she won many prizes, including the Piano Concerto Prize for her performance of Rachmaninoff's Second Piano Concerto.  Her recent engagements have included performances of Rachmaninoff's Second Piano Concerto with the Sutton Symphony Orchestra and Schostakovich's Second Piano Concert with the Orchestra of the London College of Music. 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. The Concerto for Piano and Orchestra in G minor, Op. 33, is the only piano concerto by Czech composer Antonín Dvořák.  Written in 1876, it was the first of three concertos that Dvořák completed, followed by the Violin Concerto, Op. 53 from 1879 and the Cello Concerto, Op. 104, written in 1894–1895.  The piano concerto is probably the least known and least performed of Dvořák's concertos. Pyotr Ilyich Tchaikovsky's Piano Concerto No. 2 in G major, Op.  44, was written in 1879–1880.  It was dedicated to Nikolai Rubinstein, who had insisted he be allowed to perform it at the premiere as a way of making up for his harsh criticism of Tchaikovsky's First Piano Concerto.  Rubinstein was destined never to play it, however, as he died in March 1881.  The premiere performance took place in New York City, on 12 November 1881.  The soloist was Madeline Schiller, and Theodore Thomas conducted the New York Philharmonic orchestra.  The first Russian performance was in Moscow in May 1882, conducted by Anton Rubinstein with Tchaikovsky's pupil, Sergei Taneyev, at the piano.
Answer: is notorious for being one of the most difficult pieces in the repertoire.