I haven't recorded "You Must Believe Me" before (because I didn't know any parts), and I still don't know many parts. I'm pretty confident about this guitar part (which is only three pitches), but that's it. I'm dubious about the bass part, and while I think I learned the chords, I can't even approximate a correct rhythm, so I left them out entirely (I think it's just B, E, and F# though).
I've mentioned before that I have a Curtis Mayfield & the Impressions anthology, which includes the original version of "You Must Believe Me," and I plan to listen to that sometime in the next few weeks. Hopefully hearing the original will be enlightening.
