The second "long" in the line "Sometimes I spend long nights long regrettin'" is sung with a melisma (E D), musically giving a sense of duration.
I'm still going under the assumption that the Moodies based their version of "Don't Let Me Be Misunderstood" on the Animals' version. Not only does the Animals' version not feature a melisma'd "long," but the line itself is quite different. In the Moodies' version, the line "Sometimes I spend long nights long regretting" is present in the second and third verses (I'm not very confident in my transcription, and there's one line I can't even make out in full):
Sometimes, babe, oh, I feel so carefree
With a joy it's hard to hide
Sometimes I spend long nights long regrettin'
If you hurt me [???] down inside
Oh, oh, baby, don't you know I'm human
With thoughts like any other man
Sometimes I spend long nights long regrettin'
Some similar little stupid thing that you've done
In the Animals' version, these verses are:
Baby, sometimes I'm so carefree
With a joy that's hard to hide
And sometimes it seems that all I have to do is worry
And then you're bound to see my other side
Oh, oh, oh, baby, don't you know I'm human
Have thoughts like any other one
Sometimes I find myself long regretting
Some foolish thing, some little sinful thing I've done
I might not even have my transcription of the Animals' version right. It might be "Sometimes I find myself [a]lone regretting." In any case, the melisma'd "long" for duration seems to be unique to the Moodies' version.
