I've only done random colored strips and mitered the corners. My strips were 2 1/2 x 6 1/2. Is mitering the corners fun? No. Is it visually worth it? Yes, IMO.

[ATTACH=CONFIG]533967[/ATTACH]
This was my first attempt at piano keys. I kind of like doing them, as it's a great way to use up scraps. Thinking most any size that works for you is good.

For me using corner blocks, either solid or pieced is easiest.

I think you can make them any width/length you think will look good on your quilt. If I've used 2 1/2 squares in the quilt, I will use that size. If I use 4 or 5 inch squares, I will just make the piano keys half that size. Be sure to show us your finished quilt.

the easiest corner is to put in a 'solid' square. If you decide to miter and it doesn't match exactly, alter a couple keys along the side. A small difference there will be less noticeable than at the end.

Love your quilt jc. And the "zipper" border is great. Thanx for the tip

Your quilt is beautiful!

I like piano key borders. Make sure that you measure your quilt top through the center both ways, ease the borders in and then you won't have wavy borders.
I make my pieces varied widths, other times I make all the pieces the same width. Sometimes I just want to use up scraps, the borders are usually 4"-6"; it depends on the quilt. I sew the top and bottom borders on first and then the sides, I don't miter my borders.
Sharon in Texas
quilting since 1988

I have had trouble reading these posts due to left out words and misspelled words. Sorry for the complaint, but maybe we need to proofread more closely.

Thank you all for the great advice, I too have wondered about how to do this. Your pictures and advice help so much!