I found slippery elm a help for a throat slightly feeling I might cough if I sang.
I'd sent off for Singer's Secret, a spray of Aloe Vera I think. I binned it as spraying it as directed MADE me cough. With it were free samples of Thayer's Slippery Elm tablets that you suck (several flavours that all tasted the same, not unpleasant) and I reckoned these helped a voice not quite right (though then drinking water would have washed away the coating).
The packet said available in health stores but I couldn't find them, maybe in the States.