Question: Gustav Mahler composed a beautiful piece performed by the Bach-Elgar Choir. What is the name of that piece??

Context articles: Gustav Mahler in Toblach
Piano Quartet (Mahler)
Mahler (film)
Bruce Carey
Gustav Mahler: Dark Flame
Symphony No. 6 (Mahler)
Symphony No. 2 (Mahler)
Bach-Elgar Choir
Gustav Mahler Jugendorchester
Symphony No. 1 (Mahler)

Gustav Mahler in Toblach (subtitled I Went Out This Morning Over the Countryside) is a live album by pianist Uri Caine's Ensemble featuring compositions by Gustav Mahler recorded in Italy and released as a double CD on the Winter & Winter label in 1999.
The Piano Quartet in A minor (also referred to as the Piano Quartet Movement in A minor) is an early work of Gustav Mahler, the intended first movement of a piano quartet that was apparently never completed.
 It is the only surviving piece of chamber music without voice composed by Mahler.
Mahler is a 1974 biographical film based on the life of composer Gustav Mahler.
 It was written and directed by Ken Russell for Goodtimes Enterprises, and starred Robert Powell as Gustav Mahler and Georgina Hale as Alma Mahler.
 The film was entered into the 1974 Cannes Film Festival, where it won the Technical Grand Prize.
Bruce Anderson Carey (16 November 1876 – 8 May 1960) was a Canadian choir conductor, baritone, and music educator.
 He began his career in Hamilton, Ontario, where he notably founded the Bach-Elgar Choir in 1905.
 After directing that ensemble for seventeen years, he moved to Philadelphia, Pennsylvania in the United States where he was conductor of two famous choruses: the Mendelssohn Club and The Bach Choir of Bethlehem.
Gustav Mahler: Dark Flame is an album by Uri Caine featuring interpretations of music by Gustav Mahler which was released on the Winter & Winter label in 2003.
Symphony No. 6 in A minor by Gustav Mahler is a symphony in four movements, composed in 1903 and 1904 (revised 1906; scoring repeatedly revised).
 Mahler conducted the work's first performance at the concert hall in Essen on May 27, 1906.
 It is sometimes referred to by the nickname "Tragische" ("Tragic").
 Mahler composed the symphony at what was apparently an exceptionally happy time in his life, as he had married Alma Schindler in 1902, and during the course of the work's composition his second daughter was born.
 This contrasts with the tragic, even nihilistic, ending of No. 6.
 Both Alban Berg and Anton Webern praised the work when they first heard it.
 Berg expressed his opinion of the stature of this symphony in a 1908 letter to Webern:
Symphony No. 2 by Gustav Mahler, known as the Resurrection Symphony, was written between 1888 and 1894, and first performed in 1895.
 Apart from the Eighth Symphony, this symphony was Mahler's most popular and successful work during his lifetime.
 It was his first major work that established his lifelong view of the beauty of afterlife and resurrection.
 In this large work, the composer further developed the creativity of "sound of the distance" and creating a "world of its own", aspects already seen in his First Symphony.
 The work has a duration of eighty to ninety minutes and is conventionally labelled as being in the key of C minor; the "New Grove Dictionary of Music and Musicians" labels the work's tonality as C minorE♭ major.
The Bach-Elgar Choir is a community chorus of long standing in Hamilton, Ontario.
 The Choir is composed of accomplished amateur singers from Hamilton and neighbouring cities of Burlington, Oakville, Mississauga and Simcoe.
 Notable performances by the ensemble include the North American première of Verdi's "Requiem" and the Canadian premières of Górecki's "Miserere" and Mahler's "Symphony No. 2" (the Resurrection).
 The choir has had several distinguished directors throughout its history and has performed in several notable venues including Roy Thomson Hall in Toronto, the Brantford's Sanderson Centre, with the Buffalo Philharmonic Orchestra, and at the Boris Brott Summer Festival.
 The choir enjoys frequent guest appearances with the Hamilton Philharmonic Orchestra.
Gustav Mahler Jugendorchester (GMJO) (in English, Gustav Mahler Youth Orchestra) is a youth orchestra based in Vienna, Austria, founded in 1986 by conductor Claudio Abbado.
The Symphony No. 1 in D major by Gustav Mahler was mainly composed between late 1887 and March 1888, though it incorporates music Mahler had composed for previous works.
 It was composed while Mahler was second conductor at the Leipzig Opera, Germany.
 Although in his letters Mahler almost always referred to the work as a symphony, the first two performances described it as a symphonic poem or tone poem.
 The work was premièred at the Vigadó Concert Hall, Budapest, in 1889, but was not well received.
 Mahler made some major revisions for the second performance, given at Hamburg in October 1893; further alterations were made in the years prior to the first publication, in late 1898.
 Some modern performances and recordings give the work the title "Titan", despite the fact that Mahler only used this label for two early performances, and never after the work had reached its definitive four-movement form in 1896.