Tails but no pins?

I often look at Mathias Wandel's website and Youtube channel to see the latest of his many ingenious devices, which are sometimes whimsical and sometimes practical.  You don't often come across someone designing and building wooden bandsaws that actually work well.  He is clearly a clever and creative individual.

As much as I enjoy seeing what he does, I don't find too much of it applicable to my hand tool woodworking, but this week was different.  After cutting a test joint on the table saw dovetail jig he is working on, he got the idea to round the corner and, when he did, a remarkable result occurred.  He started with this:

and ended up with this:

Photos used with permission.  Read about it and watch his video here.

This came as a total surprise to me; I am just amazed.  Given that woodworking is millennia old, it seems quite likely that someone has discovered this before, but I have certainly never seen or heard of it.  It is as if there are two sets of rounded tails and no pins at all.  There's no endgrain.  To me it looks like the interlocked fingers of two hands.  Now that I have seen it, I can understand why it looks this way, but I never would have guessed.  I find it aesthetically appealing and quite suited for many contemporary pieces.  There is something very attractive about the melding of the straight lines of the dovetails with the curve around the corner, a sort of complex simplicity for lack of a better way to describe it.  In addition, I think the joint is quite eye-catching because it is unusual and it is not apparent how it goes together after the joint is assembled.

This joint reminds me of a weekend course I took with Andy Chidwick in which he demonstrated how he makes the curved, flowing joints of his rocking chairs, which are similar to those made by Sam Maloof.  Oversimplifying, you create the joints while the pieces are in rectangular form and then shape the joined pieces after they are assembled.  Andy does this with power tools, an angle grinder in particular, but I think the technique is particularly well-suited to hand tools.  You can imagine the debris flying everywhere when you do this with an angle grinder and a rotary carving tool, so I left the class with a strong preference for the hand tool alternative!

The outside curve of this joint could be made with hand tools quite readily I think.  Draw in some guidelines and remove most of the material with a rasp.  (You could also saw off the outer corner before taking up the rasp.)  Finally, you can finish with a file or handplane to create a smooth radius.  The inner curve would be more difficult to make with hand tools and more work than I am willing to undertake.  As I think about the applications I have in mind, though, I don't think I would want the inside curve anyway.  A box, for example, would look just as attractive and be more functional with corners rounded on the outside and square on the inside.

Hats off to Matthias for this discovery.