I love Handel’s Messiah. Choosing a favorite piece from it is tough, but I have to say that “Hallelujah Chorus” is special to me for several reasons.
As a music theory professor, I appreciate using this piece to reinforce the concept of musical texture. The opening "Hallelujah!" section begins with a homophonic texture, with all voices singing their various harmonies together at the same time (much like a traditional hymn). Then it transitions to a monophonic one, where all voices sing the same melodic line ("For the Lord God omnipotent reigneth"). Then the piece bursts into a polyphonic texture, with multiple melodies occurring simultaneously. This chorus is great to use in the classroom to demonstrate those concepts to students.
As a music historian, I find it interesting to note that Handel wrote the entire oratorio in only 24 days and premiered it at a charity event in 1742. Reportedly, King George II was so moved by the "Hallelujah Chorus" that he stood to his feet when he heard it performed, which is why audiences traditionally stand upon hearing the instrumental introduction. While Messiah was composed as a work for the Lenten/Easter season, its American premiere was performed on Christmas day in 1818 and is still performed during Advent and Christmas.
As a former middle and high school choral director for 14 years before coming to NOBTS, I understood that no Christmas concert was complete without this piece. Teaching "Hallelujah Chorus" to many young singers over the years and making beautiful music with them is a treasure I hold deeply within my heart.
Finally, but most importantly, as a believer, singing the texts from Revelation 11 and 19, respectively, I am excited to be reminded that there is so much more to life than the troubles and pain that we endure on this earth. Hallelujah!