As someone else said...what a snarky thread. Some comments seemed to hit my insta-rage button.
<Rant start>
More than a few posts have come up with the assumption that I can't play a key change.
As some others have posted....that is a HUGE assumption.
I can whine about it if I want. Changing 75% of the tunes seems like bad song choices to me. I'll transpose whatever you want up a step and a half and play the crap out of it if you'd like.
I'll transpose it in my head if its written as well. Or play it in a different clef if you like.
Or maybe put it in different hand positions or choose a string to not use for the entire night to keep things interesting.
I'll take any of the bar tunes we play and switch modes on every chord throughout if you want me to. Then I'll write it out for you so you can play it. Unless you can only read tabs. Then maybe you need to work on your playing a bit.
I'm not here to swap discographies and credentials, so
What difficulty I have is primarily one that involves a very quick learning curve for songs, that seems to be like a tape recorder in my head.
(Photographic hearing?

)
So, when it comes time to transpose, I am hearing everything off by the interval of transposition. When I'm playing from memory, my memory is telling me that the tritone or minor second transposition I'm hearing must be wrong. I still play it, but fundamentally (no pun intended) it registers as wrong- always. That part can't seem to change in my brain.
However, it doesn't limit performance. Its totally an internal debate.
Also, I'm not being defensive, I'm just irritated by the automatic response from some posters that its a matter of inability. For some players, it may be. Try to be constructive as opposed to throwing out the typical internet anonymous response that makes you sound like a @##%er and doesn't help those who may be looking at these threads as a learning opportunity.
<Rant over>
The point isn't about what I can or can't play- its about some vocalists not realizing that they can do some work on extending their range and not having the group lear songs in one key then showing up and playing everything in a three or 4 keys.
A heads up is always good, but changing on the fly is fine for many people.
Also, I think there is a larger portion of the population out there that might not realize something has a key change applied to it, but they will realize that they don't like "the way that band sounds".
As mellowinman said:
"Fans notice when you drop the key. Oh sure, you might get away with a half step, or even a whole step, but that's about it. If you change the key a lot, you will have to do your own version of the song.
Nothing sounds lamer than a song with an iconic vocal transposed down to accommodate a mediocre singer."
I get that there are some physical limitation to the voice. Having a background that includes choral instruction helped me figure that out.

So, the need to transpose a song is understandable and necessary. As is proper song choice.
Phew. No offense intened towards anyone in the above comments. I was mainly interested in the observations of others concerning the topic.