I am training to become an opera singer. If my cords are swollen after one day of singing a lot, does it mean I’m doing something incorrectly?
The short answer is, “Yes.” The longer answer is, “Maybe not much.”
Vocal stamina has to be developed over time. If you have been singing very well for two hours a day and suddenly jump to five hours a day, the voice could be very unhappy with you. You can increase singing time by 15-minute intervals until you can sing for as long as you need to.
Professional singers learn to “mark” in rehearsals and while they are learning music. They might sing sotto voce or down the octave for 3 hours a day and then sing fully for only one hour. And so on. Timing varies from person to person.
Every voice has different abilities. Some people are never able to sing for very long periods in a single day. They have enough voice to do an opera or a recital and that is it. Others can sing for hours on end without diminishing the instrument. Some people are good at the 100-yard or 400-yard dash and others are marathoners. You have to know yourself and your instrument.
Finally, if you have any doubt about how sound your technical function is, you need to work closely with your teacher or coach. If they are telling you that swollen cords are par for the course, I suggest you consult a physician. If there is a conflict of opinion between physician and teacher, or between different teachers, you might have to choose whom to listen to.
My personal rule, after going through an awful lot, is to never stress or fatigue my voice. Period.