I don’t really care for vocals in general, but Robert Lamm with Chicago is one of a few exceptions. Peter Cetera, not so much.
Lamm, Cetera and Kath did exquisite harmonies, try "All Is Well" from Chicago V. It's easy to rip on Cetera, like people rip on Phil Collins, but Cetera was a damn good bass player, just like Phil was on drums.
Terry Kath on “Make Me Smile”.