Connection of human voice with “spiritual realities”

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 quoted by Mary L. Lucas in "A Brief Account of My Visit to Acca" (Chicago: Bahá'í Publishing Society, 1905); The Compilation of Compilations vol. II)