2 banjos, 6 guitars, 4 trombones, a euphonium, 2 trumpets, 2 saxophones, 3 basses, 1 drum set, a fiddle, a mandolin, a ukulele, an electric ukulele, a 1959 Lowry tube organ, a clarinet, 2 cowbells, 2 flutes, and a serious set of orchestral jingle bells were used to create the music in A Click Clack Moo Christmas.
Will Sheff of Okkervil River used his girlfriend's grandmother's typewriter from the 1910s to create the typewriter sounds in the song What Friends Do. Will asked drummer Jeremy Gustin to treat the typewriter like a percussion instrument and try to get as many unique sounds out of it as he could. Will also played the typewriter, so there are "dueling typewriters" playing the rhythm.
A Click Clack Moo Christmas is not the first time Rachel Bloom has voiced an animated character. She voiced Laura from BoJack Horseman and several characters on Robot Chicken.
All the instruments used to create the music in A Click Clack Moo Christmas were played by an amazing group of NYC musicians.
The composer of A Click Clack Moo Christmas, J. Walter Hawkes, is a four time Emmy Award winning composer/trombonist/ukulele player originally from Pascagoula, MS.