Question: The Song of Iowa is set to the tune of what German Christmas Song?

Context paragraphs:
O Tannenbaum: "O Tannenbaum " (] ; "O fir tree") is a German Christmas song.  Based on a traditional folk song, it became associated with the traditional Christmas tree by the early 20th century and sung as a Christmas carol.

Christmas Time (Is Here Again): "Christmas Time (Is Here Again)" (Lennon/McCartney/Harrison/Starkey) is a Christmas song recorded by the Beatles for their 1967 fan club Christmas record.  After being slated for inclusion in the planned (but ultimately scrapped) "Sessions" compilation album in 1985, the song finally saw official re-release in 1995 on the "Free as a Bird" single (issued in conjunction with the "Anthology" series), for which it was edited from its original 6:17 to a shortened version of 3:03.  The song opens with a light-hearted tune from all four of the Beatles and occasionally cuts to a tale of the Beatles arriving at the fictional BBC house.  This part of the song was cut from the 1995 single version.  The song then closes with a Christmas greeting from all four of the Beatles.  At the end, "Auld Lang Syne" is played on the organ as Lennon reads one of his original nonsense free verse poems.

Peace on Earth/Little Drummer Boy: "Peace on Earth/Little Drummer Boy" (sometimes titled "The Little Drummer Boy/Peace on Earth") is a Christmas song with an added counterpoint performed by David Bowie and Bing Crosby. " The Little Drummer Boy" is a Christmas song written in 1941, while the "Peace on Earth" tune and lyrics, written by Ian Fraser, Larry Grossman, and Alan Kohan, were added to the song specially for Bowie and Crosby's recording.

Kling Glöckchen: Kling, Glöckchen, or "Ring, Little Bell", is a German Christmas carol from the 19th century.  The lyrics were written by Karl Enslin (1819–75) to a traditional German folk tune.  According to other sources, it was set to music in 1884 by Benedikt Widmann (1820–1910).

O Sanctissima: "O Sanctissima " (O most holy) is a Roman Catholic hymn in Latin, seeking the prayers of the Blessed Virgin Mary, and often sung in various languages on her feast days.  The earliest known publication was from London in 1792, presenting it as a traditional song from Sicily; but no original source or date has been confirmed for the simple melody or the poetic text.  The tune is often called "Sicilian Mariners Hymn" or similar titles, referring to the seafarers' nightly invocation of Mary as their maternal protector: Our Lady, Star of the Sea.  The tune has been notably reused for the German Christmas carol "O du fröhliche" (O, how joyful), the English recessional hymn "Lord, Dismiss Us With Thy Blessing", and the first half of the American civil rights anthem "We Shall Overcome".

Tausend Sterne sind ein Dom: Tausend Sterne sind ein Dom is a German Christmas song.

When a Child Is Born: "When A Child Is Born" is a popular Christmas song.  The original melody was "Soleado", a tune from 1974 by (alias Zacar), composer for Italy's Daniel Sentacruz Ensemble, and Dario Baldan Bembo.  The tune was based on Damicco's earlier tune "Le rose blu" published in 1972.  The English language lyrics were written a few years later by Fred Jay (Friedrich Alex Jacobson IPI number 00015195204, who wrote many hits for Boney M such as Rasputin and Ma Baker).  They do not make specific mention of Christmas but the importance they attach to looking forward to the birth of one particular child somewhere, anywhere, suggests a reference to the birth of Jesus Christ, and the citing of "a tiny star" that "lights up way up high" may allude to the Star of Bethlehem.  Fred Jay's lyrics have been sung by many artists, most successfully by Johnny Mathis in 1976.

The Song of Iowa: "The Song of Iowa" is the official state song of the U.S. state of Iowa, written by S. H. M. Byers in 1897 and adopted by Iowa State Legislature in 1911.  The song is set to the tune O Tannenbaum and Byres' lyrics' theme is centered on his love and praise for Iowa.

Christmas Tree (Lady Gaga song): "Christmas Tree" is a song by American singer Lady Gaga.  It was released on December 16, 2008 for digital download.  It was written and produced by Gaga, Martin Kierszenbaum, and Space Cowboy, who also provides guest vocals.  Musically, "Christmas Tree" is a Christmas song with dance-pop and synthpop influences.  It samples the classic Christmas song "Deck the Halls", as well as briefly using the lyrics "Rum pum pum pum" from the Christmas song "The Little Drummer Boy" in its intro.  Lyrically, the song uses sexual innuendos.

Mariae Wiegenlied: Mariae Wiegenlied (Mary's lullaby) is a German Christmas song for solo voice and piano, with music by Max Reger and words by .  It was originally published in 1912.

Supporting paragraphs: The Song of Iowa O Tannenbaum
Answer: O Tannenbaum