Residents living in a village north of Kidlington called police after more than 200 revellers gathered at an open-air rave.
Estimates of around 200 people attended an all-night open-air session in the disused quarry at the bottom of Mill Lane, Kirtlington.
The noise and lights from the event prompted residents to complain to police about an illegal rave.
But when Thames Valley Police officers went to the quarry, they decided the event was not a rave but a private party.
They advised partygoers to turn down the noise, then left.
There were other complaints throughout the night but a police spokesman said: "We did not attend again as this was a private party.
"Any complaints about noise should have gone to the district council's environmental health department."
The fine distinction was not welcomed among regulars at the Oxford Arms pub, in Troy Lane, Kirtlington, at lunchtime yesterday.
Tim Stead said: "There were about 100 cars down the lane and the thump, thump, thump went on all night. I heard it at 11.30pm and again when I woke up this morning. We all thought it was a rave."
No-one at the pub knew who might have thrown the party.
William Long said: "We have had these things before and we all get fed up with the mess that's left. It went on all night, until the rain in the morning dampened things down."
Others in the pub said they had not heard anything, because the wind was in the wrong direction.
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