When I listened to 1967-1970 about a week ago, I thought that the guitar part in "Hello Goodbye" sounded pretty easy to figure out. Last night I figured it out, and I discovered that the first phrase is just a C major scale. I'm suspicious that I have the second-to-last note wrong though, and there are parts at the very end that I don't have yet.
I hadn't realized this until I figured out that guitar part, but in the second verse, it's replaced with the "Hello goodbye hello goodbye" backing vocals that have the same notes.