The singer of the song 'Smooth Operator' is Sade, a four-letter name. Sade is a British singer, songwriter, and record producer who rose to fame in the 1980s with her soulful sound. She has released six studio albums, with her most successful being Diamond Life (1984), Promise (1985), and Love Deluxe (1992). Her music has been described as a mix of soul, jazz, funk, and soft rock. She has won numerous awards, including two Grammy Awards, and has sold over 75 million records worldwide.