Everyone should give themselves a big round of applause for making an effort to avoid being too silly . . . And while I was vastly tempted to suggest that for choral pieces in the key of
B, the preferred lyric is "buzzzzzz", I put this patently silly thought on hold for a few days . . .
The only musical definition I found with respect to humming categorizes it as a type of "drone", which was
not a big help with respect to holding that thought, but so what . . .
Drone: Dull, monotonous tone such as a humming or buzzing sound. Also a bass note held under a melody.
[SOURCE:
Drone (Glossary of Musical Terms) ]
So what!
Overall, I think there are two strategies:
(1) Provide some type of simple instruction with the required phonetic clue(s) . . .
(2) Be as specific in every respect as possible . . .
And of course, I prefer the second strategy, since it includes the possibility of notating such things as Tuvan throat singing--one of the many types of
overtone singing--which moves the general concepts of droning and humming to a higher plane, where for reference I have been studying a particular performance of "Help!" (Beatles) toward the goal of determining whether the Beatles had a bit of FUN with the McGurk Effect auditory illusion, as well as determining whether Paul McCartney has the ability to sing two-part harmony with himself via overtone singing in real-time on the fly . . .
Overtone Singing (wikipedia)McGurk Effect (wikipedia)"Harmonic Opening" (Harmonic Chant) -- featuring David Hykes -- YouTube music video[
NOTE: In this video, I am inclined to suggest that Paul McCartney sings the word "Help!" at 0:10 in two-part harmony with himself, since something obviously happened that surprised John Lennon, causing him to do a double-take, and I do not think it was the acoustic guitar falling over in the background next to the drum riser a few seconds earlier, and while I am not certain about this, it is consistent with Lennon and McCartney routinely having a bit of FUN with switching vocal parts and at times both appearing to sing when only one of them actually was singing, which is where the McGurk Effect comes into play . . . ]
"Help!" (Beatles) -- YouTube music videoThere is an excellent video tutorial on overtone singing at this link, where the general technique is explained in just under four minutes . . .
The Choir Page (Stuart Hinds)And there is an example of one style of music notation for overtone singing shown in the following music video, where the overtone notes are diamonds and are on a separate staff . . .
"O Come All Ye Faithful" (Kiva Shimova) -- YouTube music videoDolores O'Riordan (The Cranberries) does a bit of overtone singing in the style that appears to be unique to Irish singers, although it clearly has Tuvan influences, which is yet another reason for the hypothesis that Paul McCartney can sing two-part harmony by himself in real-time on the fly, at least occasionally, which is fabulous . . .
"Zombie" (The Cranberries) -- YouTube music videoFabulous!
Summarizing, the simple approach is to include an instruction like "drone" and a few phonetic clues in the lyrics, but when the composer desires vocalists to switch to overtone singing, I think the music notation needs to be considerably more complex and specific, which I suppose could be done via using harmonic or overtone notes, if there are such things, where rather than being like standard notes, "harmonic or overtone notes" could be lighter (gray rather then black); a different color; or done in some graphic style similar to italics . . .
Lots of FUN! 