Final answer:
The piece "For Unto Us a Child Is Born" from Handel's Messiah is written for a baroque orchestra including instruments such as violins, violas, cellos, and woodwinds, along with a choir consisting of sopranos, altos, tenors, and basses.
Step-by-step explanation:
The choral work "For Unto Us a Child Is Born" is part of George Frideric Handel's Messiah, an English-language oratorio composed in 1741. This particular piece is scored for a baroque orchestra, which typically includes instruments such as violins, violas, cellos, double basses, bassoons, oboes, a harpsichord or organ for continuo, and occasionally trumpets and timpani.
The choir singing this piece would usually be composed of sopranos, altos, tenors, and basses. It's important to note that specific instrumentations can vary based on the performance and the conductor's choices, as there have been many adaptations of Handel's original scores over the years.