It turns out they're cousins four times removed. The NYT's Norman Lebrecht explains in his new book the connection goes deep, "Beyonce has presence, energy and concentration in what she does, much like Mahler...and (he) would have liked her. Mahler was interested in everything."
This was just sent to me by a listener:
The "removed" part is actually not all that difficult to understand (it's just that it's an unusual way to use the word).
First cousins are the offspring of siblings. (That's the one most people intuitively understand.) If the first cousins have children, then with respect to each other those children are second cousins. If the second cousins have children, then with respect to each other those children are third cousins (& so forth).
Okay, now for the "removed" part. This is an intergenerational term. If you have a first cousin, then you know that your cousin's parents are your aunt & uncle, but with respect to yourself, what is the term for your cousins child? The child's not your niece or nephew because that would mean he or she was the offspring of your brother or sister (not the offspring of your cousin).
No, with respect to yourself, the child of your first cousin is your first cousin once removed (as you also are with respect to the child).
Thus, if Beyonce and Mahler are first cousins four times removed that means Beyonce's great-grandparent was Mahler's first cousin.
It also appears that The Sun tabloid left out a bit of detail about the Mahler/Beyonce relation. The original tweet by Norman Lebrect says Beyonce is "an *eighth* cousin of the great composer, four times removed". http://t.co/w2Xy5M8
Now all that's left to find out is how many degrees of separation from Mahler to Kevin Bacon. I tried entering "Gustav Mahler" at the Bacon Oracle website, but Gus is not in there.
Leonard Bernstein, however, has a Kevin Bacon Number of 3. :-) jb