Sick but Singing? "Ah, the Joys of Singing in Winter....."
First take a minute and assess if you have to do the performance or not. If you are in the chorus, maybe you can back off a little bit on a song or two. If you are the soloist or lead maybe not. If it hurts when you are singing, really take a moment to re-evaluate your technique. If the show must go on.....
Take care of yourself physically. Get extra sleep, drink lots of water, wash your hands, take extra vitamin C, stay warm, avoid talking if you don't need to. Do anything that will support your immune system and get you better.
Take care of yourself mentally. Think about what you can and cannot do about the situation and get a little mental R & R. Don't go overboard with the ramifications, just make a plan.
Take some time to take an unemotional and honest look at how the sickness is affecting your voice. Sore throats often lead to a raised larynx and reduce vocal power and resonance. Swelling of the mucous membranes absorb some of your sound and affect your resonance. If the cold has gone to your chest, it may impact your ability to rapidly fill your lungs for good breath support. General aches can impair your endurance. Figure out how this illness if affecting your singing.
After you do this, make rational adjustments. Reduce your expectations a little bit. You may not sound as you usually do. Maybe that high C is not going to be as loud as you know it can be, maybe you need to add a few breaths into phrasing to help you, maybe you need to increase your support or warm up for more time than usual. It is best to get through a performance by singing on cue and in tune than worry about subtle changes. Showing up and showing professionalism is part of a singer's life and everyone will understand. In the meantime do your best to relieve your symptoms and get better so you can do your best on that day! Remind yourself that you will wake up again tomorrow and the next time you sing you will be well and astound everyone!
Many singing greats have had to make the show go on and admit they learned something from singing with a cold. Opera singer, Renee Fleming, states in her autobiography that she truly learned to sing when she was sick. She could no longer cheat on my technique and get away with it, she had to listen to her body and trust her technique to get her through.
This is not encouraging you to sing if you are very sick or if your throat hurts, but a means to help you get through it when you need to. Of course, the ideal would be to take care of yourself to the point that you never get sick (but let's be realistic, we do), but be smart if the show must go on.
Dr. Jahn's Advice (Professor of Clinical Otolaryngology at the Columbia University College of Physicians and Surgeons and author for Classical Singer):
-Make a realistic appraisal of whether you really need to sing or can cancel.
-Make an unemotional checklist of how your vocal production is impaired
-Develop a strategy for working around those impairments,
-Use medications and adjustments in technique
-Accept a philosophical attitude toward a temporary setback
Stay healthy and smart about your singing!