Songfacts®:

• This song is about a cheating couple, and the machinations they go through to keep their affair a secret. They are part-time lovers because they have to keep it on the down-low:
  
  We are strangers by day, lovers by night
  Knowing it's so wrong, but feeling so right
  
  The song ends in a twist (or maybe, a tryst), when it becomes clear to the singer that his wife has a part-time lover of her own who is playing the same game.
  
  Wonder says that he has been in a similar position, with a guy calling his home and trying to disguise his voice when Stevie answered it.
• Wonder was a pioneer when it came to making and recording music using electronics and computers. This is an early example of digital audio recording, which Wonder put together at his own Wonderland Studios.
  
  One of the devices he used was a LinnDrum, a popular drum machine/sampler. "He bought the second drum machine I ever made," Roger Linn said in a Songfacts interview. "I think he used my drum machine very well on 'Part-Time Lover.'"
• According to Wonder, he drew on two songs by The Supremes as a musical influence for this one: "You Can't Hurry Love" and "My World Is Empty Without You."
• Syreeta Wright, who was Wonder's wife from 1970 to 1972, sang backing vocals. She co-wrote Wonder's 1970 song "If You Really Love Me" and had her own Top 10 hit with her duet with Billy Preston, "With You I'm Born Again."
  
  Also featured on this track is Luther Vandross, who can be heard humming at the end of the verses.
• This reached #1 on the Billboard Pop, R&B, Dance and Adult Contemporary charts, making Stevie Wonder the first artist to score a #1 hit on four different Billboard charts.
• When this song reached the top of the US charts, it was 22 years and three months after his first hit, "Fingertips (Part 2)." At the time, this was the longest span between first and last #1s. The Beach Boys would break this record when "Kokomo" took the top spot in 1988. >>>

  Suggestion credit:
  Bertrand - Paris, France
• Wonder contributed to The Woman in Red soundtrack, released in 1984, but In Square Circle was his first full album in five years - something that didn't sit well with Motown boss Berry Gordy. Wonder was working on an important non-musical project at this time: getting Martin Luther King's birthday recognized as a national holiday in America.