Also used in numerous 19-equal songs of my own creation
12-EDO Guitar (re-tuning strings)
Xenharmonic re-tuning of 12-equal guitars is possible in a variety of ways. One way to get different equal temperaments is to use equal temperaments that share common factors with 12, (3, 4, and 6). Some examples of equal tunings that could be realized with this method are 8, 9, 16, 18, 20, 24, 30, 36, etc. Here's movement one of my first re-tuned guitar piece, Tenacious Chorale.
12-EDO Guitar (changing bridge height)
Here, I illustrate a method by which the player can change the equal temperament of a guitar by putting an object under the bridge. The taller the object, the larger the steps in the equal tuning. You can use this to get 11 and 10-equal on a 12-equal guitar (though probably not 9). Also, only the first octave is tuned accurately enough with this trick to be used in said tuning. In general, this will work for more equal tunings, the higher the EDO of the guitar used. For a 19-equal guitar, for example, I might be able to get 18, 17, or 16-equal.