Jack and Jimi: How did they do that?

I know this is a ridiculous question, but how on earth does Jack White play "Blue Orchid" on his guitar, and sing vocals that are so, um, totally different from the melody on the guitar?

A says, "Mom, Jack White practices. Hello."
I say, "Yes, but what his vocals are doing is SO DIFFERENT from what the GUITAR IS DOING."
A says, "Mom, all the great musicians do that. Look at Jimi Hendrix."

Sigh. Another reason to cite Jimi Hendrix.

I think my tombstone will read, "Herein lies the mother who so graciously bestowed upon her son his first Jimi Hendrix experience [heh], instructing him to watch Daniel Day-Lewis's magnificent performance in 'In the Name of the Father' but wherein lay Voodoo Child (Slight Return) as Day-Lewis's opening music."

Or something.