Question: The Piano Concerto No. 1 in B-flat minor, Op. 23 was composed by which Russian composer of the romantic period, some of whose works are among the most popular music in the classical repertoire?
Context: Piano Concerto No. 4 in G minor, Op. 40, is a major work by Russian composer Sergei Rachmaninoff, completed in 1926.  The work exists in three versions.  Following its unsuccessful premiere (1st version), the composer made cuts and other amendments before publishing it in 1928 (2nd version).  With continued lack of success, he withdrew the work, eventually revising and republishing it in 1941 (3rd version, most generally performed today).  The original manuscript version was released in 2000 by the Rachmaninoff Estate to be published and recorded.  The work is dedicated to Nikolai Medtner, who in turn dedicated his Second Piano Concerto to Rachmaninoff the following year. The Piano Concerto No. 1 in B-flat minor, Op.  23, was composed by Pyotr Ilyich Tchaikovsky between November 1874 and February 1875.  It was revised in the summer of 1879 and again in December 1888.  The first version received heavy criticism from Nikolai Rubinstein, Tchaikovsky's desired pianist.  Rubinstein later repudiated his previous accusations and became a fervent champion of the work.  It is one of the most popular of Tchaikovsky's compositions and among the best known of all piano concertos. 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. 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. Symphony No. 2 in E minor, Op. 27 is a symphony by the Russian composer Sergei Rachmaninoff, written in 1906–07.  The premiere was conducted by the composer himself in Saint Petersburg on 8 February 1908.  Its duration is approximately 60 minutes when performed uncut; cut performances can be as short as 35 minutes.  The score is dedicated to Sergei Taneyev, a Russian composer, teacher, theorist, author, and pupil of Pyotr Ilyich Tchaikovsky.  Alongside his Piano Concerto No. 2 and Piano Concerto No. 3, this symphony remains one of the composer's best known compositions. The Piano Concerto No. 2 in F minor, Op.  21, is a piano concerto composed by Frédéric Chopin in 1829.  Chopin wrote the piece before he had finished his formal education, at around 20 years of age.  It was first performed on 17 March 1830, in Warsaw, Poland, with the composer as soloist.  It was the second of his piano concertos to be published (after the Piano Concerto No. 1), and so was designated as "No. 2", even though it was written first. 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 ( ; Russian: Пётр Ильи́ч Чайко́вский ; 25 April/7 May 1840 – 25 October/6 November 1893), often anglicized as Peter Ilich Tchaikovsky, was a Russian composer of the romantic period, some of whose works are among the most popular music in the classical repertoire.  He was the first Russian composer whose music made a lasting impression internationally, bolstered by his appearances as a guest conductor in Europe and the United States.  Tchaikovsky was honored in 1884, by Emperor Alexander III, and awarded a lifetime pension. The Piano Concerto No. 3 in D minor, Op. 30 composed in 1909 by Sergei Rachmaninoff has the reputation of being one of the most technically challenging piano concertos in the standard classical repertoire. The Sérénade mélancolique in B-flat minor for violin and orchestra, Op. 26 (Russian: "Меланхолическая серенада"), was written by Pyotr Ilyich Tchaikovsky in February 1875.  It was his first work for violin and orchestra, and was written immediately after completing the Piano Concerto No. 1 in B-flat minor.
Answer: Pyotr Ilyich Tchaikovsky