I just got the Grateful Dead box-set "So Many Roads," which includes a rehearsal tape of "Whiskey in the Jar," recorded shortly before Jerry Garcia's demise. (It's the second-to-last selection on the album, followd by the title tune, which was recorded at the Dead's final show in Chicago.)

Jerry had just recorded the song with David Grisman for their "Shady Grove" album (which I have NOT yet heard). To my ear, he's got the melody "wrong," or perhaps "different from the traditional": the verse should have an "ABAB" melodic structure, as I recall it, with a rising or starting line, floowed by a concluding line, then a repeart of the two lines before the refrain. Jerry sings it "ABBB," with the second or "finishing" melody line repeated almost-ad-infinitum, which sounds counterintuitive to me.

However:

All such quibbling aside, it's a nice rendition, with the band gradually joining in to accompany Jerry's John-Hurt-style fingerpicking. Since it's a rehearsal recording, you hear some verbal byplay commenting on the old song. Hearing this cut prompted me to look up the lyrics on Mudcat and to stumble across this discussion thread, and I'm glad that happened.