‘In a chapel style’ is the literal meaning of the term a cappella. Today, however, it is used as a synonym for "unaccompanied." We hear about an a cappella performance of a Palestrina motet,. although it is the motet that is a cappella and not the performance. Many choral groups are called a cappella choirs, and they are proud of their unaccompanied performances of both sacred and secular works. But one cannot refrain from smiling upon hearing one of these organizations sing a madrigal with a risque text, and noting that the performance is referred to as a cappella -"in the style of a chapel." How did the "unaccompanied" connotation ever creep in?
“The term a cappella did not exist in the sixteenth century. There was no need to refer to a prevailing style by name. However, when the old and new styles were juxtaposed in the seventeenth century, a clear designation of each would have been useful. The term a cappella has a cloudy background, but it seems that Giovanni Gabrieli, in his concerted music, called the choir the cappella, in contrast to the solo and instrumental forces. It was not until sometime in the seventeen century that music for choir alone, in· the traditional style, was called a cappella.”
David Avshalomov says