RaumKlang wrote:...Drums, bassguitar, keyboards... are still playing during a guitar solo ...
Personally, I feel a lot better on stage when I'm playing a guitar.
Well, of course it all depends on the style of music and performance. There's a time to stand back in awe and show respect, and theres a time to interact with each band member.
I know the other instruments are still playing, but how? That is, are they playing what was recorded/practiced, note for note, or are they jamming until the soloist is done? If the solo is the same, every performance, then yeah, you don't have any room to improvise or participate. Get out of the way and wait your turn. On the other hand, if live is..., well, alive..., then join in! Use your instrument (your voice!), but also your brain. There are folks in the audience that are participating vicariously through the front-man (you), so you've got a lot of influence on the emotion of the performance.
In the end, I think you need to be in the moment. If the soloist is relating to the audience, and they're reacting, don't distract. When it's obvious that the interaction is waning, start interacting with the soloist (echo guitar licks, or make up a pattern on the spot and see if the soloist reacts). That can help to squeeze out more from the soloist and also provide a bridge back to the main theme. Whatever you do, don't mentally check out. If you're in front, then it's your responsibility to make sure the audience stays plugged in and entertained, so you have to make a judgement call as to whether the other guy is making a connection or needs help. Just remember, on stage you can do things you can't do 'in public' and someone is going to appreciate it.
As to feeling better with a guitar in your hands, let me tell you that I totally relate and let me share what my father told me; he asked me one day, "why do you keep singing behind that crutch?" The guitar had become a substitute for a podium, or shuffling my feet, or shoving my hands down my pockets. He then told me "Sometimes we don't respect what comes so easily. Just because singing didn't come as a struggle for you, doesn't mean it's worth less than the other instruments." So if you're holding something to make you feel more comfortable on stage, you need to throw away the crutch.