The vocal tract organ is a new musical instrument that consists of three-dimensional (3D)-printed vocal tracts (throat and mouth) for individual vowels sitting on loudspeakers to enable static vowel sounds to be produced.
The acoustic excitation from the loudspeakers is a synthesized version of the typical waveform produced by the vibrating human vocal folds during pitched sounds, which enables the instrument to be played from a keyboard.
The vocal tract organ will become an instrument in its own right, and it could be used as a direct replacement for the vox humana organ stop, given that its acoustic output is a much closer representation of the human vocal output than that from a vox humana organ pipe. The 3D-printed tracts may also be used in vocal and choral workshops as well as degree-level music technology education.
This according to “The vocal tract organ and the vox humana organ stop” by David M. Howard (Journal of music, technology & education VII/3  pp. 265–277).
Above, an illustration from the article; below, a composition by Professor Howard.