George Harrison wrote "Wah-Wah" and included it on his classic solo album, All Things Must Pass.
In September 2014, a box set of Harrison's solo albums was released and as promotion, Conan O'Brien held "George Harrison Week" on his TV show. All of the musical guests that week covered Harrison's songs. On the first day, Monday September 22, Beck was the guest, and they did "Wah Wah."
Beck also played it once at his own concert a week later, but it did not last in his repertoire.
Video of the Conan appearence seems to be gone now, but here is audio: