I don't know if there's a video of a performance of the Brahms, but if you go to the Carnegie Hall KZfaq page there are a series of videos of Shaw preparing choruses for several masterworks, and the first 2 videos are of his prep work for the German Requiem. I'm a singer, and have sung the work a few times, and so I appreciate the "nuts 'n' bolts" of the Shaw preparation videos. By far the best video I've seen of the Requiem has disappeared here on KZfaq: it was the Danish Radio Orchestra and Chorus with Herbert Blomstedt. A VERY close rival to Shaw's recording.

Good news! The marvelous Blomstedt performance with the Danish Radio Orchestra is back on KZfaq (I’m writing this on September 17, 2023.) It is my favorite, too. Here’s the link: kzfaq.info/get/bejne/kJOYjdGVrpbThIk.htmlsi=kCG_4KrDZ9Lrpz0q _(I also left a comment with complete English & German texts + time stamps.)_ 😎🎹