According to this wiki, "Song of Hope" (희망가 Huimangga) is adapted from "The Lord Into His Garden Comes", also known as “When We Arrive at Home”, a hymn by 18th century American composer Jeremiah Ingalls. The book Excursions in World Music (Nettl & Rommen 2017) describes it as “a representative example of this dizzying colonial process—based on a Japanese popular song that was modeled after an American hymn, which in turn was drawn from an English folk tune.”
The Japanese song is called “Lament of Shichirigahama” (七里ヶ浜の哀歌, Shichirigahama no Aika) or, from the first line of lyrics, “Ridge of the Pure White Fuji” (真白き富士の根, Mashiroki Fuji no Ne), written in remembrance of middle school students that died in a 1910 boat accident. Here’s an old 1935 recording. It has been translated to Taiwanese (in local dialect).
The first Korean recording of the song was done in 1925 by two gisaeng, as part of an album named “These Troubled Times” (이 풍진[風塵] 세월[歲月], Yi Pungjin Sewol, lit. “The Wind-and-Dust Years”), a collection of translated Japanese songs and one of the first pieces of popular music in Korea. Since then, many versions have been made in different styles, mostly taking on a slow 6/8 ballad rhythm: examples are a broadway-like rendition in 1936 under the name “Souvenir of Buddy”; then as “Song of Hope”, a 1977 trot song (and another in 1989, and another in 2013); a sensible folk-rock cover from 1984; An’s soulful acoustic version from 2006; and a classical interpretation by an opera soprano in 2020 (who also sang a really interesting contemporary arrangement of Arirang in the same album). The first line, “이 풍진 세상을 만났으니, 너의 희망이 무엇이냐” (Yi pungjin sesang-eul mannass-euni, neoui huimang-i mueos-inya), which means “In the face of these troubled times, where might hope lie?”, is known by many Koreans and strikes a resonant chord within them.
The song seems to remain popular today in Korea and Japan, regarded as a classic that’s often associated with grief and memories, even though the original hymn has become somewhat of a distant memory for Americans. A Japanese video uploaded in 2014 has accumulated more than 1 million views. The 2017 period film The Battleship Island, depicting an attempted prison escape from a forced labor camp in Japan-occupied colonial Korea, included “Song of Hope” as its ending song. A recent performance on TV show Mr. Trot once again revived interest in the ch’angga song. Various other fairly recent covers can be found: 2002, 2014, 2015 p’ansori version by Jang Sa-ik, 2020 daegeum solo.
Maybe this can be a useful case study connecting the dots to the origins of Korean popular music. It's very interesting to see how one melody evolved through time, and how despite the different contexts and narratives tied to each of the Korean and Japanese versions, as well as the multitude of names it has taken, they all convey a similar feeling. Here’s a playlist I will keep updated that collects the versions I found in a somewhat chronological order.