So the 50 Big Ones version of "Isn't It Time" is actually 10 seconds longer than the iTunes single. Looks like the iTunes version has a slightly more sped-up tempo. What's up with that?
This intrigues me. As I believe I noted in another thread, the BBC-streamed version was digitally time-compressed. That is, a tempo "speed-up" but with no pitch change. I had assumed it was their doing. Now, maybe that's not the case after all? Is the iTunes version moving along quicker than the 50 BO's version but still in the same key as well?
Just as a quick FYI, for folks who actually care about these little things...

I did finally do a direct comparison the iTunes EP version of the single version of "Isn't It Time" to the BBC version. They're the exact same time-compressed "sped-up" version (although with the radio airing fading out a bit early). Which makes perfect sense now, because lo and behold, there's now a 1-track CD radio station promo of the track floating around where it's referred to right on the disc as the "Radio Edit." This is obviously the disc that was supplied to the BBC all those weeks ago for its radio debut.
Again...this is the same 3:38 version that's on the iTunes EP -- digitally time compressed to move the track along at a quicker tempo while keeping it in the same key. (i.e. not an "analog-type" speed-up). It's *not* time-compressed on 50 Big Ones.
Call me a heretic, but I actually like this time-compressed "Radio Edit." It "peps" the track up slightly without making everyone sound like a chipmunk. Sort of ironic too, in that, like the very first Capitol single of their career, the potentially last Capitol single of their career has had its speed tweaked, too, in a released form (with the first one obviously being an analog speed-up and pitch change). Symmetry!
In conclusion:
"Isn't It Time" - single version
50 Big Ones - 3:47
"Radio Edit" - 3:38 (digitally time-compressed)
Edit: Listening again to both versions, there *may* be a bit of "analog-type" speed-up as well. Going back and forth...I honestly can't tell. Any changes in pitch are virtually imperceptible. At least to my 4:30am ears they are...lol.