In mechanical speech synthesis reed pipes were mainly used for the generation of the voice. The organ stop "vox humana" played a central role for this concept. Historical documents report that the "vox humana" sounded like human vowels. In this study tones of four different "voces humanae" were recorded to investigate the similarity to human vowels. The acoustical and perceptual analysis revealed that some though not all tones show a high similarity to selected vowels.
Bibliographic reference. Brackhane, Fabian / Trouvain, Jürgen (2013): "The organ stop “vox humana” as a model for a vowel synthesiser", In INTERSPEECH-2013, 3172-3176.