This clarinet arrangement of Jolly Old St. Nicholas is in the key of concert B flat (key of C for the clarinet). Select the image below for a printable PDF of the melody. The Jolly Old St. Nicholas Band Play-Along page has more versions of this song, so you can play it with other woodwind and brass instruments. The string arrangement of the carol is in the key of concert C. Visit the Jolly Old St. Nicholas main page which features the carol in many different keys. On that page you can find an instrumental range that is comfortable for you, or print an arrangement that allows you to play along with string instruments.
See the transposition page for explanations and charts to help you determine the appropriate key for each instrument.