Peer review of your work
Hi there,
Your article is well-written thus far, and for the most part I found it to be informative, objective, and comprehensible. I found the structure of your article to be easily-understandable, as you start off with the basics (i.e. what overtone singing is) before moving into the techniques and scientific phenomenon of the matter.
I would suggest that for some of the descriptions you give regarding how overtone singing is achieved, you consider creating diagrams to help the reader visualize what it is that you are describing. For example, when you say that "adept overtone singers achieve the desired effect through altering the shape of the vocal tract", it may be helpful to include a visual representation of exactly what sorts of tract shapes produce certain sounds. You also state that "Singers will change the shape of their vocal tract in order to align the frequency of a formant with that of a harmonic, therefore causing the overtone to resonate more strongly and create a perceivable change", and your inclusion of links to the wikipedia pages for "formant" and "harmonic" was helpful, however I think that a more in-depth explanation of what it means to "align the frequency of a formant with that of a harmonic" would be even more beneficial.
Similarly, in the section about the scientific phenomenon in overtone singing, you state: "Studies have suggested that the distinct clarity and strength of the sung overtones are a result of Helmholtz resonance within the vocal tract". It might be worth elaborating on which studies you are referring to (if you refer to them at all in the article) and elaborating on exactly how Helmholtz resonance manifests itself in the vocal tract (this is another place where diagrams could be helpful).
In general I would suggest slightly lengthening each part of your article with more detailed descriptions of the scientific processes you are analyzing, as it will help your reader understand the ideas you are portraying in a more substantial way, and it will help bring your article's word count up to the 1000-word minimum.
Generally though, I think that this is a good draft and it is for the most part informative and digestible for the reader. Good work.