Mark Murphy's rendition of "Stolen Moments"
https://www.youtube.com/watch?v=UsvTPeAYfuATerry Kath, the great guitarist from the band Chicago (one of my favorites) and vocalist on many of their songs, has a similar tone. When I heard Murphy the first time I immediately thought of Kath.
The great Terry Kath on guitar on lead vocals. The piano intro ends at about a minute in and he starts singing (for all you jazz fans not familiar with the song).
https://www.youtube.com/watch?v=3UOP6l82vU0Chicago has always been one of my favorite bands of any genre all time. First "big band" rock group using a brass section to break into the pop charts regularly but at the same time not "sell out" and still play great innovative music that you cant really "categorize"
Terry Kath's vocals engineered in a studio:
https://www.youtube.com/watch?v=cWkXmx-0phc