SoundTouch

• Filter Length: anti-alias filter length (8 .. 128 taps, default: 64). How "spread out" should we be trying to smooth things?
• Sequence Duration: This is the default length of a single processing sequence in milliseconds (default: 40), which determines the how the original sound is chopped in the time-stretch algorithm. Larger values mean fewer sequences are used in processing. In principle a larger value sounds better when increasing pitch, smaller value sound better when decreasing pitch.
• Seek Window Duration: The seeking window default length in milliseconds (default: 15, but kJams sets default to 50), for the algorithm that seeks the best possible overlapping location. This determines from how wide a sample "window" the algorithm can use to find an optimal mixing location when the sound sequences are to be linked back together. The bigger this window setting is, the higher the possibility to find a better mixing position becomes, but at the same time large values may cause a "drifting" sound artifact because neighboring sequences can be chosen at more uneven intervals. If there's a disturbing artifact that sounds as if a constant frequency was drifting around, try reducing this setting. I found that a value of 15 causes "choppy" sound, and a value of 50 makes it much smoother.
• Overlap Duration: Overlap length in milliseconds (default: 8). When the sound sequences are mixed back together to form again a continuous sound stream, this parameter defines how much the ends of the consecutive sequences will overlap with each other. This shouldn't be that critical parameter. If you reduce the Sequence Duration setting by a large amount, you might wish to try a smaller value on this.

More technical details from the SoundTouch page.