Just the two of us by Bill Withers has a moderately difficult bass line that’s also very creative. What makes it so unique is how the various notes outside of the typical key blend with the song effortlessly. The verse bass line is the same as the intro but an octave below. The end of the song showcases an opportunity for a bass slap performance with embellishments if you wish. If you want to learn more about Bill Withers, see his Wiki.