Help with Gershwin / Jewish Heritage question

[nmitchell076]

Okay, so I am playing the Concerto in F by Gershwin.  Since this is my first large concert piece, and it is one that I have until next fall to learn, I'm diving into the research pile on this one.  In the book, "George Gershwin: His Life and Work," there is a passage which reads "Lazare Saminsky... found in the piano concerto (presumably the opening solo theme) 'something which might adorn the mystic dreams of the young Talmudist-student from the Dibbuk-legend.'"

Would any Jewish scholars like to fill me in on what specific Dybbuk (since that's what I assume "Dibbuk" is a misspelling of) legend is being referred to here?  I always thought Dybbuks were just like ghosts in our modern culture (IE, part of the folklore, but no overarching defining legend regarding them).  Am I wrong? Is there a specific legend being referred to in this passage? Or am I reading it all wrong?

I appreciate any advice you can give on this subject.