The march is the third movement of Chopin's Piano Sonata No. 2 in B-flat minor, Op. 35. Chopin wrote the march first, in 1837, and built the sonata around it two years later; it was published in 1840. The march frames a gentle, singing middle section in D-flat major, then returns.
Robert Schumann, reviewing the sonata, wrote that Chopin had bound together four of his maddest children. The march soon took on a life of its own: an early Brussels edition printed it on its own, with a title saying it had been performed at the composer's funeral, and it has been played at funerals and memorial ceremonies ever since, often arranged for brass band or orchestra.
This transcription: Chopin, Piano Sonata No. 2 in B-flat minor, Op. 35 (1840), third movement 'Marche funèbre', bars 1-10: the melody transposed to A minor and up an octave, the left-hand chords reduced to two notes: Forty Piano Compositions, ed. James Huneker (Boston: Oliver Ditson, 1903), p. 181 - archive.org fortypianocompos00chop, page n204; checked against the Meynne edition (Brussels), archive.org marchefunbreex00chop, page n3.
Transcribed by GOONS Studio from the original work, which is in the public domain.