Locally we have a radio station that has a classic lunch hour—meaning, they play some songs from the sixties through the early eighties from noon to one o’clock. Yesterday, I heard “Let’s Groove” by Earth, Wind & Fire. That song just so happens to be their biggest R&B hit-topping the chart for eight weeks back in 1981. At the time, I loved that song so much—as a big fan of Earth, Wind & Fire (they were my favorite band at that time)—they could do no wrong. But now, in the cold light of history, I feel bittersweet about the song. Because I can see now, what I couldn’t see then—”Let’s Groove” was the last real high point for the group. Everything that followed signaled the decline of my favorite band—not that they didn’t have any hits. There were a few more hits that followed—but nothing that reached the highs the…