What does 'a cappella' literally mean?

Answer

It means singing without instruments.

Context

The phrase is Italian. Cappella means chapel, and Britannica glosses a cappella as in the church style; in the manner of the chapel is the same idea. It describes polyphonic vocal music performed by unaccompanied voices, and it first referred to sacred choral works.

The style took shape in the late 15th century around composers such as Josquin des Prez and peaked in the late 16th century with Giovanni Pierluigi da Palestrina, whose music for the Vatican's Sistine Chapel is a key example of Renaissance church music. By the 17th century, a cappella writing was giving way to the cantata, which had parts written specifically for instruments.

Here is a historical wrinkle. Later scholars saw no independent instrumental parts in this repertoire and assumed the choirs sang with no accompaniment at all. Newer evidence suggests that an organ or other instruments often doubled some of the vocal lines, so the modern meaning of strictly instrument-free singing is partly a later reading of the old term.

Today the term covers secular music as well, including barbershop and recorded vocal-only pop. Dictionaries also list the single-p spelling a capella as a variant, although a cappella with two p's reflects the Italian.