What actually happens when we yodel is very interesting or so I think. I am referring to typical voice shaking in Indian music (not hollywood) . I will refer to it as Yodeling; I do not know what else to call it.
You can hear it below.
After some help from Prabha and repetition when I was reasonably satisfied that I can use the sample (I recorded above), I plotted it.
You can see that here:
The findings are simple:
a) There are many types of Yodeling and what we see here is a constant tone yodeling
b) I think there are two keys, D5 and D6; one key each from 2nd and the third Octave (two lobes in the left side of the plot)
c) Because we create two volume levels with two dominant keys we get an envelope that looks like superposition of two sine ways in that key (frequency) (approx).
d) Most important thing is that the lower volume level tone corresponds to higher octave key and the higher volume level tone to the lower key.
You can see the wave form here:
There are different types of yodeling as I we know. The one shown above is a single tone yodeling. It is possible to change tones while yodeling (melody). What changes along with it is the envelope (volume) of keys.
The kind if yodeling used in a music sometimes sets it apart from other kinds of music. So will, amount of non-dominant tone suppression (sharpness of tone), voice timbre (me or you) often used attack/line/decay sequence of notes (note inflections) and typical sequence of notes reused in many melodies (Gamaka). Correct me and add to this post if you happen to have found more about these things.