Let me start by saying that out of the tree ways to refer to the part of your body that generates sound, there is only one that is the anatomically and medically correct terminology and that is vocal folds.
There’s another one that is not as technical but still ok to use, and one that is a misspelling of the latter and being the educated choir singer that you are, you want to avoid using. So, which one’s the culprit?
The absolutely medically correct terminology is vocal folds. Thanks to tiny cameras that doctors use now-a-days, we know that we produce sound for speaking and singing when air causes two tiny membranes in our throat to vibrate, much like the skin of a drum.
These membranes are called folds because they are made out of layers of mucous membrane much like phyllo dough on top of baklava. Don’t let the word mucous throw you off though (I know it’s not a pretty word, so let me use mm from now on).
An mm is called so, not because of what it produces, but because of its purpose in the body. These are membranes that protect all internal parts of the body that come in contact with the environment. So for example, the lining inside your mouth is also an mm.
But, who’s going to win in the battle of chords vs cords! If you want to impress others and look like the awesome chorister that you are, read on.
The less technically correct, but still ok word to use is cords; so vocal cords. I’m sure you want to know why that is, and why vocal chords is wrong, so here’s the story of how this came about.
It was 1741, when Antoine Ferrein, a French anatomist (he would probably be called an otolaryngologist today), came up with the term cordes vocales or vocal cords (doctors wrote in Latin at the time) to refer to the vocal folds. His idea was that vocal cords were the same as the cords of a violin or a guitar. I found this image that I think is close to what he had in mind.
As, you’ve figured out, vocal chords is the wrong one, even if you hear it and read it with the same frequency as vocal cords. It is pretty confusing taking in consideration that chord is a perfectly valid musical term.
A chord is a group of two or more notes sang or played at the same time, as when a choir sings a song. The most popular use is probably when people refer to guitar chords. The confusion probably comes from the use of the word chord in geometry to refer to a line that links two points on a circle. But let’s not blame math, now.
So, use vocal folds and vocal cords, and as for vocal chords, that would be you and two more of your choir buddies singing a 3-note harmony.