I officially sang with a band-using no lyrics! Always wanted to do it, but always was scared I'd clam up and forget the words. I have sang once with another band but looking at a lyric sheet. And I have sang karaoke, on stage, with the band playing along with karaoke music.
It started out one of the band members came to me, during their break and said the owner asked me to sing. I was like

!! He said or you can just play a song on bass. So I played a song on bass, and then after a while came back up and sang Loretta Lynn's You Ain't Woman Enough. I had to sing out the song so that they knew what key. It was a slower paced but they pulled it off and I did too without a mistake!
Reminded me of the first time I played bass with the band..thought I'd forget the words! hehe!