In Funkify Your Life by the Meters (and many other Funk tracks I've heard), the guitar line blends with a vocoder effect. You can hear it in the first 30 seconds here on YouTube.
How was this achieved back then and has anything changed with modern recording techniques?
That would be a Talk Box (the track referenced in your questions is listed on the Wikipedia page).
The gadget works by having a small loudspeaker linked by plastic tube to the musician's mouth, allowing the shaping of notes with the mouth, much as a singer would.
There is a nice clip on YouTube of Peter Frampton using such a device.
