I gather one of Joseph Smith's widows wrote a number of Mormon hymns.
I was interested to discover that the Mormon Tabernacle Choir began when Brigham Young heard some Welsh converts singing, and asked them to organize the choir. He said, "I can't understand the words, but I love the music." So, they must have been singing in Welsh.

Martin Luther was baptized, posthumously, into the Mormon church some time ago, so, I suppose, his hymns are now Mormon hymns.