諸經要集 4.41

4.41

如長阿含經云。其有音聲五種清淨。乃名梵聲。何等為五。一者其音正直。二者其音和雅。三者其音清徹。四者其音深滿。五者周遍遠聞。具此五者乃名梵音。

As the Dīrghāgama says: When a voice has five kinds of purity, it is then called a Brahmā voice. What are the five? First, its sound is upright. Second, its sound is harmonious and elegant. Third, its sound is clear and penetrating. Fourth, its sound is deep and full. Fifth, it is heard all around and far away. Possessing these five, it is called a Brahmā voice.