Before I actually started singing solo in public myself I was given to understand that it was polite practice to listen to the verses, and join in with the choruses ... but no more than that. A practice I normally adhere to, unless invited to "join in if you know it" by the singer.

Since I have started singing out myself I can see why it is rude to do otherwise. I have invested a fair bit of time (usually) in coming to grips with a song, it's meaning, it's emotional content, and the way best to present it (obviously that particular aspect is always going to be a subjective and very personal thing). The song has become very personal to me, and when I sing it I am concentrating on many facets of it - meaning, content, breathing, phrasing, best way of delivering it. I had an experience some months ago of standing up to present a serious and sad ballad, and had got half way through it... arriving at a very emotional point I was suddenly beset by what I can only describe as a strident mooing from the front row. One of the audience had decided to join in with me . Firstly, it threw me, and I promptly forgot my next line; secondly, it ruined the mood for me and chucked me out of the song (so to speak), and I spent the next three verses listening to the lowing and mooing getting noisier. It added nothing to my presentation, but it certainly added to my irritation levels! On yet another occasion I was delivering a slightly more well known song, which hopefully I had crafted and made my own, only to find an experienced singer, relatively well known in the area as a semi-pro, suddenly joining in with me - with bad harmonies. Again, irritation city... I had worked hard to make the song (not a chorus item) mine, and the delivery of it had been carefully thought out. Her insertion into it completely broke it's mood.

As far as I am concerned, it's a very rude thing to do and an absolute no no ... and there should be absolutely no need for the singer to tell people not to join in ! Good manners should tell them that.