I have an eclectic taste when it comes to music. I love classical, jazz, r&b, blues, soul, rock and roll, jazz fusion and yes, funk
I love Chicago and Terry Kath. Kath is one of my favorite guitarists. I would not say he is underrated, at least not by musicians or guitarists, he just died, sadly, way to young (don't ever play with guns)đ
I have plenty of Eddie Harris CDs in my collection. Same with War, Kool and the Gang, Tower of Power, Sly, and yes I have one Larry Graham CD which happens to be "Graham Central Station" (I do not like the opening track, "We've Been Waiting"). But I would not categorize Graham as jazz/funk, its more like pop/funk.
Have you ever listened to the great jazz trumpeter and composer, Donald Byrd's jazz funk recording sessions, 1969-1973. 6 good to very good albums (depending on the listener). Here is Byrd's 1971 release called "Ethiopian Knights"
https://youtu.be/Ofa8VEkCnFQ?si=QnJBEIBMx-8r1L5V
Another great jazz musician, guitarist Grant Green, recorded a few jazz/funk albums as well. Hear is a live album that is a killer jazz/funk session:
https://youtu.be/f2y3vttWeNU?si=4d_OAsIM3uFYryZS

