I've now watched every video of Bessie Jones on YouTube, and there is ALWAYS clapping, ALWAYS on the offbeat. "Sometimes" just doesn't have the foot-stomping to tell us where the 1 and 3 are. We have to internalize it. Check out the videos:
But here's the meat:
Historically, music from the African-American tradition (spirituals, gospel, blues) and its descendants (rock and roll, hip hop) accent the offbeat. It might be harder to make distinctions between "black music" and "white music" today, but in Bessie Jones's time, this would not be the case. Simply, those with experiential basis in the African-American tradition would feel the offbeat, and those with experiential basis in the Euro-American tradition would feel the opposite. Today, nearly all music is syncretic. Maybe I feel "Sometimes" the way I do because I listened to nothing but ska and reggae from fourth to tenth grade (very strong accent on the offbeat), and maybe Dr. Amico listened to a lot of Russian opera. Who knows. But anyway, watch the following video clip. Look at the way the children clap. The white children immediately start clapping on the beat, and the African-American girl claps on the offbeat. Eventually, Bessie starts clapping on the offbeat, and all the children correct themselves (to the best of their abilities). This is not a racist observation. In those highly segregated times, less cultural syncretism would lead to differences in the races' treatment of music. In the most politically correct terms I can think of, Dr. Amico and Moby are just too white to hear the clapping on the offbeat!
I hope I've made my point without being too offensive or confrontational. It's all in the spirit of debate!