I think I heard Glen Campbell say he actually played bass on Wichita Lineman but that the intro and bass riffs in the song were Carol Kaye’s ideas. It might not be too complicated but her contribution is the main reason that is one of my all times favorites. Am I misremembering? Did she actually play on the recording? I think, other than Hal Blaine, she might still be the most heard musician in music history.
She came up with the lead into Wichita Lineman. Glen Campbell borrowed her bass guitar for the instrumental riff on the song. It was a Danelectro bass that she had customized for the unique sound Glen really liked.
That song features a solo played on a 6 string bass, which is unusual. My guess is that the intro bass line was Carol Kaye’s idea and the solo was Glen Campbell’s creation, and GC probably played both.
Here’s an interesting live performance of Wichita Lineman:
https://www.youtube.com/watch?v=4qoymGCDYzU
The backing instrumentation is prerecorded but his vocal and the 6 string bass seem to be live.