1. O Come, All Ye Faithful
While the origin of the words remains uncertain, the melody is credited to John Reading (1692), an English composer and organist at Winchester College. In 1751, John Francis Wade, an English priest and music copyist working in France, combined the Latin words with Reading's music resulting in the hymn known in Latin as "Adeste Fidelis". It was first publicly performed in London at the Portuguese embassy and thus it became known as the "Portuguese hymn" 
 

2. Angels We Have Heard on High
The words began as a poem by James Montgomery which he printed in his newspaper on Christmas eve in 1816 in Sheffield, England. The melody was composed by a blind composer and organist, Henry Smart. The original title, "Regent Square", was named after the location of St. Phillips Church where Smart was organist.  The words and music were first published together in a collection of carols in 1855. 
 

3. It Came upon a Midnight Clear
When American composer Richard Willis (1819-1900) composed this melody he referred to it as "Study no. 23." Coincidentally, in the same year (1849), Edmund Sears (1810-1876), a minister in Wayland, Massachusetts, wrote  words for a Christmas song reflecting upon that winter season and the sobering reality that the country was on the verge of civil war. With that background, the glorious song of "peace on earth, good will toward men" takes on added significance.  The words and music were joined together in 1850.  
 

4. Away in a Manger
Although sometimes known as Luther's Cradle Hymn, there is no basis for the legend that Martin Luther both composed and sang it to his children. The song originated in America in the mid 1800's.  It remains an anonymous carol considered a traditional, universal Christmas lullaby telling the story of the nativity with gentle and sweet imagery. While the words have been set to several different melodies, one of its  most popular settings  is Flow Gently Sweet Afton which has been incorporated into the introduction of this instrumental arrangement.
 

5. O Come, O Come, Emmanuel
This melody has its origin in a Gregorian Chant.  The version we are most familiar with came from Thomas Helmore, who in 1854, adapted this haunting melody from a Latin hymn.  The words go back 800 years to a style  called Plainsong from the days before written music. It was often sung without harmony or strict meter by monks in the seven days leading up to the Christmas service. On each evening the song would be sung, a different Biblical name of the Messiah would be substituted in the opening verses including Emmanuel or Immanuel  meaning "God with us" according to the  Old Testament prophecy  (Isaiah  7:14 and  9:6).
 

Answers  6-10

6. We Three Kings
The words and music were both composed by John Henry Hopkins (1820-1891). Hopkins was a poet, composer, church rector, and designer of stained glass windows.  This carol was one of several he wrote for an annual children's Christmas pageant. Though written in 1857, it was thought to be taken from an anonymous medieval composition because of its unusual style and combination of modes. This arrangement is performed on the high strung acoustic guitar.
 

7. O Holy Night
Adolphe Adam (1803-1856) was a French composer of several stage and ballet productions. He took his melody to his close friend, the French poet Cappeau de Roquemaure who supplied the lyrics. They titled their collaboration "Cantique de Noel." The English words we use today were written by an American clergyman and musical scholar,  John Sullivan Dwight. Adam's composition was initially met with criticism from French church officials who denounced it for its "lack of musical taste and total absence of the spirit of religion." It has gone on to become one of the most popular works in the repertoire of popular and sacred holiday music.
 

8.  Hark ! The Herald Angels Sing
The lyrics are attributed to Charles Wesley in 1730.  Felix Mendelssohn wrote the music 100 years later as part of a celebration commemorating Gutenberg, the printer. The melody and lyrics were joined together by English musician William Cummings in 1855.
 

9. God Rest Ye Merry, Gentlemen
Its actual meaning is  God keep you, gentlemen, in merry spirits. The true origin of this carol has never been established, however, it was likely a popular London street song and was  even mentioned in Charles Dickens' A  Christmas Carol.
 

10. Silent  Night
On the day before Christmas in 1818, Joseph Mohr, a young associate minister, brought a poem he composed to Franz Gruber, the church organist, to be set to music.  Since the organ was broken, the two finished and performed the song that night using a guitar for accompaniment. The organ repair man finally showed up in the spring. While testing out the repaired organ, Gruber performed "Silent Night".  The repairman, after hearing the song, was so impressed he took a copy of the hymn to his town.  From there it was passed on to a traveling musical group and its popularity spread throughout the world. In 1863 it was translated into English and became an American favorite.