The choir director obviously does know how to direct a choir.
He repeatedly flails his arms no matter what the choir should be doing.
While Andy is explaining his plan to the choir director, the audience hears Olan Soule's dubbed voice say "But Glen Cripe is not a tenor" apparently because the producer or someone realized the inconsistency of the soloist being a bass and had to explain it.
Andy flubbed his line while explaining the "sensitive" mic to Barney but catches himself and corrects it.