Where Does Audiosurf Put Corkscrews?

Color shifts and track steepness are determined by the intensity of the song. However, I find that corkscrews are placed seemingly randomly. What determines their placement?

EDIT: Adding a bounty because the only two answers are a bit lacking in evidence.

Solution 1:

After playing for a while, I'm now under the impression that corkscrews are in fact placed completely randomly in the song. Unlike other people who seem to only encounter them at intense moments of songs, I may have actually encountered MORE of them in the least intense moments of songs (intro, outro), in addition to some others which seemed arbitrarily placed throughout tracks.

However, given that on any given track, the corkscrews will always be in the same place, there must be some sort of operation going on that determines their placement, but I'll be damned if I have a clue what it is.

Anyway, this was too long for a comment.

Solution 2:

All I can say is that I have never seen them on easier difficulties but they sometimes show up on harder difficulty levels in fast/intense tracks.

They really should make these more common since they are really cool ^^