the choir typically uses '' satb '' voices ( soprano or treble , alto or counter-tenor , tenor , and bass ) , though in many works some or all of these voices are divided into two for part or all of the piece ; in this case the two halves of the choir ( one on each side of the aisle ) are traditionally named decani ( or 1 , for the higher voice ) and cantoris ( or 2 , for the lower voice ) .