Chapter V-I. Choir, Organ, and Other Musical Instruments
274. In relation to the design of each church the schola cantorum should be placed so that its character as a part of the assembly of the faithful that has a function stands out clearly. The location should also assist the choir's liturgical ministry and readily allow each member complete, that is, sacramental participation in the Mass. 
275. The organ and other lawfully approved musical instruments are to be placed suitably in such a way that they can sustain the singing of the choir and congregation and be heard with ease when they are played alone.