What term describes unaccompanied choral singing?

The correct term for unaccompanied choral singing is "A Capella." This term originates from Italian, meaning "in the manner of the chapel," and refers specifically to vocal music without instrumental accompaniment. In A Capella performances, singers rely solely on their voices to create harmony and melody, which highlights the quality of the vocal performances and the interplay between voices.

In contrast, the other terms listed do not apply to unaccompanied choral singing. "Fortissimo" refers to a dynamic marking indicating that the music should be played or sung very loudly, not to the structure of the performance. "Solo" describes a piece of music performed by a single singer or musician, which is not representative of a choral group. "Chamber" typically refers to small ensembles or groups of musicians, often including various instruments, rather than focusing solely on vocal performances without accompaniment.