I was delighted to learn from a tweet by Lyonette Louis-Jacques, the International Law Librarian at the University of Chicago (and a Slaw columnist), that two of Karl Llewellyn's lectures are available in audio on the U of Chicago website. Llewellyn was an adherent of the U.S. "legal realism" movement and, perhaps most famously, the force behind the drafting of the Uniform Commercial Code.
One of his duties at Columbia, and later at the University of Chicago, was to deliver introductory lectures to first year students. His book The Bramble Bush, still read with pleasure today, came out of this duty. Karl Llewellyn died in 1962.
In the former, you'll hear his forceful, indeed hectoring, voice hammering home to students the difficulty of practice and the importance of the duty each will have to clients. Some of what he says may be dated — he snaps at a student not to smoke — but the majority of it would benefit any law student, and not a few of the rest of us, perhaps.