Snopes is very generous giving it a "mixed" rating...
http://www.snopes.com/critters/gnus/cricketsong.asp
-But the real trick is almost certainly described at the end:
Critics contend that Wilson didn't simply slow down a continuous recording of crickets chirping; they interpret his statement that he "slowed down this recording to various levels" and Bonnie Joe Hunt's reference to Wilson's "lowering the pitch" several times to mean that he used multiple recordings of crickets, each slowed down by a different amount to produce a specific pitch, and layered them to create a melodic effect sounding like a "well-trained church choir."
Certainly, the recording has been around for quite a while, but only recently (within the last couple of years) have I seen the added text that this only occurs when it is slowed down by an 'absurd' amount (slowed by something like 200 times, I seem to recall). -If it really WAS slowed down by 192 times, frequencies in the ~1kHz region would have to have been captured at 200kHz. Information at 3kHz would have to have been recorded at 600kHz This gives the lie to the whole thing of course...
Yes, we WANT to believe that insects "sing" in a reverential manner, and that stunning beauty lies beyond our perception... and this is why we so readily fall for this trick.
For the truth, you don't have to slow anything down. -Just listen to crickets. -They tend to chirp at a single note. -In fact there is a formula to tell you the temperature by the center frequency of this note, and it has been long known.
For the crickets to sing a "scale", either the long-known formula would have to be nonsense, or someone has manipulated the crickets. A sampler is easy to do, and you can -very truthfully- tell people that "all you're hearing is crickets slowed down" and be telling the technical truth. -It sounds beautiful, and people then are sufficiently impressed to remember it, and repeat tales of the "beauty".
But it's a deception, unfortunately... -well, the "scale" or "Melody" is. -Slowed-down crickets to me do indeed sound beautiful, but then so do regular-speed crickets. (unless I'm trying to record an acoustic guitar outside at night!)
Keef