I adore harpsichord and clavichord and am always in awe of accomplished organists.
mr dave - ABBA (the band) probably has nothing to do with deriving itself (themselves) from the form. According to wikipedia, ABBA's the name of a Swedish fish-canning company. But the parallels are un'can'ny
Call-and-answer type music has been around a while. Perhaps the fugue is a great illustration of it, and that's a great observation. For what it's worth, I think modern call-and-answer comes from the gospels and American slave songs.
I know rock has a long lineage from the hands of Blues, Folk, Country, Swing, and Gospel music. Perhaps its ties into the gospel branch gave it that element. But call and answer is a varied form or Imitation, which has been around since at least the baroque period. After all, fugues are imitative monsters, and you nailed that on the head with your observation.
Fugues differ from the concept of a lead line over the clunk-a-clunk of accompaniment by the element of all voices (in this case, parts) would be the melody and the accompaniment and everything else. You could argue that the main voice (the one to start off the fugue) is more important than the others, but that argument is easily lost as the piece progresses.
In jazz and rock and all, normally you have one lead (usually guitar and/or voice in rock, usually trumpet/sax/voice in jazz), and everything else is strictly a background instrument. There's never (ok, rarely) any trade off to other instruments. Even in a drum solo, usually the guitars and other instruments stop playing altogether.