Could it have been audio from a TV channel 6 some place? In NYC, we have a low power "TV" station that broadcasts at 87.7[5] MHz (WNYZ TV- LP -- see
http://en.wikipedia.org/wiki/WNYZ-LP). For example, "On many FM radios, the audio for analog channel 6 can be picked-up by turning the tuner dial below the lower FM band edge, at 87.75." Note from this chart (all frequencies in MHz) :
Channel Lower edge Video carrier ATSC pilot Audio carrier Upper edge
6 82 83.25 82.31 87.75 88
Since the upper edge is 88 MHz, maybe your transmission was some channel 6 audio carrier run slightly amok? Didn't mention lyrics, but was it THAT racy?

(Nowadays, a lot of stuff may slip past would be censors....)