Voice is the vibration of the air, and is like the waves of the sea. The voice is produced through the instrumentality of the lips, throat, teeth, tongue, etc. These cause a wave in the air, and this wave reaches the nerve of the ear, which is thereby affected. This is the voice.
There are two kinds of voices. One when the complete instrument is perfect, then the emission of sound is perfect. The second is when the instrument is imperfect, it affects the voice in such a way that it is far from pleasing. What we have just said refers to the voice itself….
In the world of existence physical things have a connection with spiritual realities. One of these things is the voice, which connects itself with the spirit; and the spirit can be uplifted by this means -- for though it is a physical thing, it is one of the material, natural organizations -- therefore, it is effective…. ('Abdu'l-Bahá's words to Mrs. Mary L. Lucas, as quoted in 'A Brief Account of My Visit to Acca’, pp. 11-14; The Compilation of Compilations, vol. II, Music)
