JHW, I understand Bill's original line in exactly the same way - they were on their way to play to an audience of people they had never met but whom they already thought of as friends. To me that sums up very neatly and concisely the special intimacy of folk clubs.

Singers alter songs, both consciously and unconsciously. It's important to make a song personal to you. Some changes don't really matter and may even help if it makes it easier for you to deliver the song. However when the writer has come up with a carefully worded and apposite phrase (as I think this one is) I think a change should be avoided if possible, and only be made after very careful consideration.