I think you can if you want, but if you have a soft voice, male or female, and are trying to lead a pack of loud voices, it will not be well received usually. If you have a pack of quiet voices, it does not matter..sing at will. Know the culture of the group and know where your voice fits..if it is a large group, let the leaders lead and shine somewhere else. Now, as to changing the gender/sex whatever the rule is, please try very hard not to do that. It is very annoying to me and I presume others. We expect one version and hear another. I think it never improves a song. At the very least say you have changed it. Also..man changes woman to man in song. next woman hears it and thinks i can't sing like a man and changes it to woman..on and on. song gets mangled.