Abstract: The invention includes in one form a sewing machine, two trackers (mice) to track the ends of material-to-be-joined, and a controller for controlling stitch formation to achieve precise control of the material position, permitting desired easing (positive or negative). A long table is preferably used with a separation plate so that the two panels-to-be-joined can be laid out flat and separated during sewing. The mice slide in tracks so they will move in a straight line. The mice are adapted so that tension can be maintained and that the mice can be pulled back when the seam is done. Optical encoders are used so that the position of the mice, and thus endpoints of the panels, can accurately be determined. The sewing machine has an attachment that provides differential feed of the two plies in response to the desired and actual position of the stitches.