From Tim Page's introduction to The Glenn Gould Reader:
"… he liked to sing along—loudly—while he played. Gould apologized for this quirk: 'I don't know how anyone puts up with my singing, but I do know that I play less well without it.'"
Perhaps elsewhere Gould apologizes, per Mr Page. But the Respectful Opposition point out that I don't know how anyone puts up with x, is not apologizing for x. It's a concession that x is objectionable.