Apart from nursery rhymes etc I never sang until my voice broke - for some reason after that event I acquired the ability (is that too strong a word) to sing in tune. First song to an audience was certainly a rugby song which would have been learnt as a youthful caver (as opposed to rugby player)in the Mendips.    Something like 'Ring the bell, verger'.
In a folk club (it would have been Redditch), I wish I could remember what the first one was - theres been a lot of years and songs since then.