I sewed this many years ago (15 years maybe) out of knit scraps, just for fun. Here it is displayed next to an instrument my husband made. Here are more of his guitars.
Emma is helping me spread out the cape. The shape was dictated by the size and shape of the scraps.
Here is the other end. I couldn't get the whole cape in the picture.
I simply overlapped the fabric pieces, zigzagged and then I trimmed any excess. That way it looks tidy on both sides.
Here is the back or inside. The binding was attached with a zigzag also. Knit doesn't unravel, so the raw edges aren't a problem.
The appliques are all from the same print knit. I think they tie it all together. It was really fun and free to sew. You could use the same technique to make smaller scarves (I did that too).