This viola music to In Dulci Jubilo is in the key of C. Select an image below for a printable PDF of the melody. The In Dulci Jubilo string play-along page has more versions of this carol, so you can play it with violin, cello, and bass. The band version of In Dulci Jubilo is also in the key of C, so you can play along with woodwinds and brass instruments. If you are looking for a different key or instrumental range, the lead sheet page for In Dulci Jubilo has versions in seven different keys, in treble, bass, and alto clefs.
See the transposition page for explanations and charts to help you determine the appropriate key to play in when performing with instruments that are not in concert key. More Christmas songs for viola.