Watch the The Vocal Cords online guitar lesson by Karan Andrea from Guitar Player Wanted: Vocals A Plus
Your vocal cords are simply folds of tissue that sit horizontally across the opening of your larynx. It is very important to understand that their movement is to open and close horizontally from the back to the front of your larynx. Almost every untrained singer instinctively reaches 'up' for high notes, when in fact, there is NO vertical movement in your cords at all for high or low notes - it's all horizontal back to front, front to back. Therefore, the note you are singing is determined by how far open (or closed) your vocal cords are, and the tension you create across them. This combination of position and tension is very much like fretting a note on your guitar, except that your voice is "fretless."