I started a thread here years ago called something like, "I'm sorry, but...." and then I had a rant about the pre-emptive apology (as instanced in the opening post). Yes, yes, and yes to all of that!

It simply unnerves the audience and makes them suspect they're not going to enjoy the song. Some will be thinking, "Well why doesn't he sing one he does know?" or "So why hasn't she practised it and found the right key?"

Fair enough to include a caveat if someone has requested something you weren't planning to sing; fair enough to apologise after a song if something did go badly wrong. But when you're presenting something of your own choice, try to make it sound as if it's going to be worth listening to.

This does not mean you have to extol your own talents. The song is what it's all about, and it may help to give a pointer or two to the aspects that you like or consider important. This does NOT mean telling the whole story, but giving a hint such as "I like the way she answers him back when he gets cocky," or perhaps a brief explanation of an important dialect or archaic word that will be used. Just a few words explaining why this song is special for you can make it more enjoyable to listen to, and help people focus on the strengths of the song.

But don't apologise before you've even begun.

Marje