One (or the only) CO 767-400's spent most of Saturday doing touch and go's at SWF (Stewart Airport) in Newburgh, NY. I was working outside in my yard and had it pass overhead about once every 5 minutes for a good portion of the day. It is one of the smoothest sounding aircraft I have ever heard. There is a significant "whistle" sound to the engines as they spool down. There was also an NY ANG C5 Galaxy also doing some practice turns at the same time, so it was a good "heavy" day at SWF. Can anyone fill us in on the details of the practice flights?