Tommy Cogbill played the guitar part on Aretha Franklin’s Think. Posters on the Soulful Detroit blog are discussing what a great guitar part this is – there are questions about who the guitarist was but this poster gets it right:
I checked my Aretha box set last night - it credits the guitarists on "Think" as Tommy Cogbill and Jimmy Johnson. As Phil says Jimmy is a rhythm guitarist, he's on almost everything Aretha recorded for Atlantic in 67-68 almost always with another guitarist who's presumably the lead. "Think" was recorded April 15th 1968 in a five day run of sessions (4/14 to 4/18). Jimmy Johnson's on almost every track recorded, Tommy's on three or four. So it looks as if it's definitely Tommy. Bobby Womack was not on any of the April sessions, nor was Matt Murphy who as far as I know only played on the film version of "Think". I'd say that pretty much nails it.Jimmy is playing quarter note chords throughout the verses while Tommy is playing the lead. Technically, Tommy's part is an obbligato (defined as a persistent but subordinate motif) being played behind Aretha's magnificent vocal. It's subtle but great stuff!
Click on the arrow to listen to the audio (click again to stop):