Ok, so about a day or two ago I was watching a band play and the bass player was adding these "wooo wooo" sounds into the song. I've heard players do it before but I can't figure out what notes they play to make it happen... It seems to be a chord that shifts down a half step then back up a half. He was doing it up past the 12th fret position. I know the description is somewhat vague... I will try to find an example of someone playing it. A possible example is on American Idol, the bass player on there would use it from time to time.