Thanks for that, Foolestroupe and Jim Lad. I try not to sing too near the limit of my range in any case, to avoid going flat at the high end. It's just that I find increasing the volume can help reach the higher notes, and conversely, if I sing notes near the bottom of my range, I find I'm unable to sing them at such a high volume. This applies when I am singing unamplified. I guess I shouldn't try to sing louder just because there's no amplification.

With a mic it's OK, because obviously I don't need to sing as loud to be heard. Then I can sing in a lower key.

Maybe I do need lessons or something, but I don't know who to go to or where I'll get the time. Meanwhile I'll just try not to sing too loud!

(Foolestroup, not sure why you put the alcohol comment in between mine, that was from someone else!)