I have some live music from Porcupine Tree and I noticed something strange in one of the live versions I have of a song called "Dislocated Day" by Porcupine Tree. Every once in a while Colin Edwin will make some weird higher pitched sound, that I can only describe as sounding like a drop of water.
I'm REALLY curious how he makes this sound. I know he is using a fretless here but not sure how he does it.
http://www.youtube.com/watch?v=gOOaHdzzHxs
Somewhere between 4:05 and 4:15 he does a really nice one, but he does it at other parts throughout the song.