I adjust the key of any song to suit my vocal range and then play in that key, whatever it is.

I can usually play any song I know in whatever key is required should someone else be singing.

Whilst I've never really analysed this scientifically, I don't remember songs as discrete chord sequences in a specific key, I seem to remember them as relative intervals from a start point.

I have no idea if this is strange although a guitarist friend considers this as some form of magic!