Payan is a serious piece, though I guess not all *that* mainstream. I would think it would have wider appeal than the trio/quartet of Parker, Lovens and Kowald, however. There is a solo album of Monk and other standards as well, I think, though I'm blanking on its title.
Man, I'm at a loss for straight-ahead Shlippenbach records... the Schoof on CBS is pretty straight, from '66, though that hasn't been reissued on CD unfortunately.