IT all depends on the circumstances of the performance.

IF I have paid out something in excess of the price of two pints of beer I expect a certain standard in return. As posted above that can be a less than brilliant rendition of something I can join in with or something worth keeping quiet to listen to.

If I am paying a premium on top of that for a major performer topping the bill I expect the support spots to be of a quality to reflect what I have paid.

At an informal singaround then you take pot luck.