Steely Dan are great, I dunno if I'd say they qualify as keyboard-based in the same way Sparks do but lyrically they definitely fit.

Deceptive Bends is the "half" I was referring to. Some fantastic tracks on that album, but also some I don't care about at all. (the "half" could also refer to the 10cc-in-all-but-name "You Didn't Like It Because You Didn't Think of It" which isn't as good as their main 4 but not worth being as overlooked as it has been). Bloody Tourists is decent, but I almost never feel like listening to it. At that point in their career I switch over to G&C's albums which are more 10cc than 10cc were at that point. Consequences basically sucks (1LP of mediocre-to-decent material buried in 3LPs of pure boredom), but L, and Freeze Frame are both wonderful, and even their 80s stuff is at least interesting even if it's not always great.