This page includes two versions of the trumpet music for What Child Is This? One is a solo version in a slightly easier key of G minor (concert F), and one is in the key of B minor (concert A) which allows you to play with other band instruments. The string arrangement of the carol is in the key of E minor. Visit the What Child Is This? lead sheet page which features the carol in seven different keys. There you can find your desired instrumental range, or print an arrangement that allows you to play along with string instruments or the recorder.
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 trumpet.
What Child Is This? version for trumpet and other wind and brass instruments: