A Dictionary of Music and Musicians/Chapelle
CHAPELLE, originally the musicians of a chapel, and now extended to mean the choir or the orchestra, or both, of a church or chapel or other musical establishment, sacred or secular. The maître de chapelle is the director of the music. In German the word Kapelle or Capelle is used more exclusively for the private orchestra of a prince or other great personage, and the Kapell-meister is the conductor or director. Cappella pontificale is the term for the whole body of singers in the Pope's service, the cantatori cappellani, the cantatori apostolici, and the cantatori pontificali.
The word 'capella' is said to be derived from the cape of S. Martin, on which solemn oaths used to be taken. Thence it came to mean the building containing the cape, and thence the musicians, also the vestments, and the vessels of the building.[ G. ]