082 / The Original Soundtrack by 10CC, 1975
"I'm Not In Love" has an interesting story:
"[Eric] Stewart came up with the idea for the song after his wife, to whom he had been married for eight years at that point, asked him why he didn't say "I love you" more often to her. Stewart said, "I had this crazy idea in my mind that repeating those words would somehow degrade the meaning, so I told her, 'Well, if I say every day "I love you, darling, I love you, blah, blah, blah", it's not gonna mean anything eventually'. That statement led me to try to figure out another way of saying it, and the result was that I chose to say 'I'm not in love with you', while subtly giving all the reasons throughout the song why I could never let go of this relationship." [via Wikipedia]
The Wiki pages also goes on to say that the originally recorded version of the song was considered trash by the other bandmates and abandoned. Stewart eventually persuaded the group to give the song another go but this time recorded it with just their voices.
YES. JUST. THEIR. VOICES. Watch a portion of the 10CC documentary explaining the crazy way they created "I'm Not In Love" on YouTube... it's such magic.
Since it's release in 1975, it has had an everlasting popularity.