Unless you are an art quilter you probably don't vary the texture in your fabric but keep it in mind as an option you can use. In 1979 100% cotton fabrics could be find while various fabrics used for clothing and home decorating were readily available. Quilters were still cutting their fabric with scissors. Modern rotary cutters and cutting mats would come along in the 19 80s.
Use your own judgment on whether you want to angle your strings or make them straight. You may choose to make the strings all the same width or vary the widths. Use modern or reproduction fabrics as you please or even mix them.
You don't even have to sew the strings on a foundation though if you are using a variety of sized and angles sewing on a base of paper or fabric might make it easier. Don't feel restricted by rules as string quilts always varied a great deal. That's why string quilts are a great way to be creative while using scraps.
String quilts can be sashed or not as you see in the examples near the top. You can put strings on just part of the block making the other part plain. The variation to the right using bright colors with black as the background is an example of this. It looks complicated but it's just one of the many variations you can create by where you put the strings and how you tilt the blocks.

Think about other blocks that can be adapted to strings. Some can be completely pieced but others are more easily appliqued on as with the stars shown to the left. You could even make the background of strings and applique a motif on top of that.
So put on your creativity hat and enjoy using some of your scraps in an string quilt.
Reference:
* p 18 "String Quilts 'n Things" by Marjorie Puckett