 Among the number one hits of 1977 was one Marvin Gaye wrote and recorded under protest. His record label wanted him to get into disco, which Marvin felt was music without substance. But finally, Mr. Gaye came up with a song he first called Dancing Lady. That title got changed to Gotta Give It Up. If you listen carefully near the end, though, you can hear Marvin playing a glass bottle halfway filled with grapefruit juice. I do not lie.