We never really know/bother what specific key we are singing in.
However, we have a start note and sometimes, for some songs, it takes quite a while to determine that note. Some of this is a "Range" issue, some is not. A difference of a semi-tone sometimes makes a song sound/feel right to us (3 of us Sop Alto Tenor in choral range) I wish I knew why. What the correct start note does though, which I can explain is "I don't get really dirty looks from the Alto"
Would someone who knows these things like to address the differences of major and minor key sounds, cos that does make a difference.