I translate a short excerpt (p.75) from the most famous German method for chorus: Basiswissen Kirchenmusik 2 (Chor- und Ensembleleitung), ie Fundamentals of church music, volume 2 Conducting of choir and ensemble), which moreover defines ecumenical text, because it is intended to churches of various denominations.
Vocal choral training
The song is a gift to humanity. Only man can lead immediately to the expression his emotions and his feelings and express themselves artistically singing.
Singing is a holistic event for both the singer and the listener.
A singer who presents an happy song convincingly see happy faces in the audience and even if the text has not been understood.
Conversely, it has effects on listeners when a choir sings only forced and loud. In a relatively short time, the public will react with discomfort, lose interest, you will cough and clear your throat.
Voice and mood are directly related to each other.
In speaking and singing the individual becomes a person (from the Latin personare, resound through something).
Even in language use reflects the fact that the use of the voice is always about the whole person: be willing, to get better or worse, determine, agree, to assent - all examples of holistic and communicative part of the voice.
The work on the voice so is always work on the whole person, body and soul.
So far my translation. Particularly interesting, in the original German, the pun between Stimme (voice) and Stimmung (mood), with various derivations verbal wohlstimmen (which I translated as: being willing), bestimmen (to determine), abstimmen (to agreed), zustimmen (to assent).