On the Similarity of Tones of the Organ Stop Vox Humana to Human Vowels

In mechanical speech synthesis from the 18 up to the 20 century, reed pipes were mainly used for the generation of the voice and the organ stop vox humana was central in this process. This has been described in different historical documents which report that the vox humana in some organs sounded like human vowels. In this study, tones of four different voces humanae were recorded to investigate their similarity to human vowels. The acoustical and perceptual analysis revealed that some, though not all, tones show a high similarity to selected vowels.