"It's a Sin" is a song recorded by English synthpop duo the Pet Shop Boys which reached number one on the UK Singles Chart for three weeks in 1987, and was their third top ten in the US when it reached number nine on the Billboard Hot 100.

Written by Chris Lowe and Neil Tennant, "It's a Sin" was the lead single from the duo's second studio album, Actually. Released in June 1987, it became the duo's second UK number one single. It was also a massive hit across Europe, supposedly the best-selling European single of 1987. In the United States it reached number nine on the Billboard Hot 100 chart, becoming the duo's third Top 10 hit there. A demo of the track was first cut in 1984 with Bobby O, and the song's form in the demo remained intact to the final version, although the released production is far more dramatic.

The song is a description of Tennant's Catholic upbringing and education at St Cuthbert's High School in Newcastle upon Tyne, implying that everything that is perceived to be pleasurable in life is regarded as sinful. The song uses extensive samples from Latin masses (specifically, Tennant reciting a part of the Confiteor, and other sounds recorded at locations such as Westminster Cathedral) and religious imagery throughout to reinforce the feel of the song. Tennant has said that he wrote the lyrics in 15 minutes, purging his emotions in a moment of frustration and anger.

The Latin passage near the end translates as, "I confess to almighty God, and to you, my brothers, that I have sinned exceedingly in thought, word, act and omission, through my fault, through my fault, through my most grievous fault".

...
Wikipedia