All the new opera houses and theaters are rectangular. This shape also best suits the presentation of drama since it facilitates staging. In round churches, after construction is completed, a sound engineer is called in to install a sound system. The system has to compensate, usually with limited success, for the dead space. As a result, congregational singing dies.
Many parishes end up with a choir director or cantor urging parishioners to sing louder.
The people, even if they are singing their hearts out, cannot fill the church with music. The building absorbs their voices like a sponge. An additional reason to build longitudinally is that a rectangular church- makes the best use of sunlight. The strongest architectural element in one of these structures is the ceiling. The only way the sun enters the space is through a hole in the roof.