For a scrubbing effect, you could try this:
• Select a sample in the Sound Browser
• Disclose the Gallery & click the Gallery Button
• In Sources, play Scrub Control
• Control the amount of scrub-effect by adjusting !ReleaseScrub
If this is the effect you are looking for, you could edit the Sound and copy the 'scrub' TimeIndex input to the SampleWithTimeIndex, and use this as the timeIndex for your buffered MemoryWriter recording.