This is really cool. I used to do a lot of overtone ("harmonic") throat singing and playing with this tool reminded me of those days.<p>For anyone curious, vowels are mostly just how we perceive different harmonic distributions. Put differently, harmonics are the basis of what it means to pronounce a different vowel. The human voice is basically just a harmonic chord, with different distributions of the 2nd, 3rd, 4th, etc. harmonics.<p>e.g. <a href="https://www.open.edu/openlearn/health-sports-psychology/health/from-sound-meaning-hearing-speech-and-language/content-section-2.3" rel="nofollow">https://www.open.edu/openlearn/health-sports-psychology/heal...</a>