I am making a piano key border for the first time right now. For the corners I am using a 1/4 log cabin for the corners. I found this on the internet from someone's blog from the UK. She had a couple other ideas, but I don't remember her blog's name. I did a search on Google, so maybe you can find the site too. My piano keys are many different colors from the quilt, so I didn't think a miter would look good. Would post a picture, but I don't know how. I'm lucky that I can post here since I am computer challenged. lol
Sue