Final answer:
The term 'a cappella,' originating from church music traditions, specifically refers to singing that is unaccompanied by instruments.
Step-by-step explanation:
The term "a cappella," which has roots in church music traditions, refers to singing that is unaccompanied by instruments. This style of music harkens back to religious settings where the focus was on the human voice to convey the melody and harmony of the piece.
A cappella Sistina originally meant the style of singing used in the Sistine Chapel, where instruments were not used to accompany the choir. In today's usage, "a cappella" usually indicates vocal performances where singers perform without any instrumental backing. Furthermore, its relation to 'long meter' hymns also signifies its traditional use in an unaccompanied manner in religious congregations