Slurs in most notation software do seem to be “just” cubic Bézier curves, but I sometimes wonder why nobody has introduced more control points. Certainly an extra point in the middle would be a nice addition to transition between the current range of shapes and “flat” slurs. I guess finding a simple way for non-mathematicians to understand how to control the shape is part of the problem. (Come to that, I also wonder why nobody uses a mathematical formulation where all four control points are on the slur itself…)
Unfortunately, I don’t have access to Dorico, since my trial has expired, so I can’t do a direct comparison of slurs. But I am actually talking about something else:
I was able to adjust the settings in Dorico so that the shape and fullness of the Dorico slur in general was quite close to that of Finale, which was encouraging. But when slur contour must be corrected on an individual basis, I found that it takes a much more effort in Dorico to the point where it becomes impractical to achieve the same overall results as in Finale. I couldn’t really understand why except for the reason I mentioned: one seems to be able to adjust the slurs at too fine a level in Dorico, so that the slur can be too easily misshapen. In contrast, slurs remain effortlessly smooth and beautifully contoured as one adjusts them in Finale.
But, of course, one can produce very bad results in Finale if the default settings are not corrected; but this is very easy to do.
I only mention this because I hope that Dorico will improve to the point where I can eventually use it.
I meant no disrespect to whichever bright mind has programmed them. But obviously the true difficulty does not lie in drawing the shape but rather in figuring out where to draw it.
I don’t know, as long as you can drag something around it’s just a matter of practice, isn’t it?
I wasn’t implying any disrespect. But I rather suspect that the choice might sometimes have been made on the basis of “that’s what other apps do” rather than thinking it through from first principles. Of course a cubic Bézier curve is about the simplest thing that looks (approximately) like a conventional slur, and can also represent some types of S-shaped slur.
Yes, but some things are more intuitive than others. For example, you could devise a system for controlling the shape of a Bézier curve where all the controls were attached to the end points only (e.g. you define the direction and curvature at the ends to control how much the slur “balloons” from a straight line). But it wouldn’t be very intuitive!
All this gets more interesting when you want a friendly way to define multi-segment slurs. One day I’m going to write a note about that - there has been a lot of research done (going back 50 years to the earliest CAD systems) about how to create multi-segment splines which visually “look smooth.” It’s not just a matter of avoiding “kinks” in the curve (which is what Dorico does) but also about grading the changes in curvature. A slur made from a straight line and two circular arcs at the ends would look completely wrong, for example, because the curvature suddenly jumps from one value to another.
No flat ties yet, but there are flat slurs so you could fake it using them as long as you didn’t care about playback. It would be a pain if you had a lot of them to do though.
Thank you! Yeah, I really don’t want to resort to such Hacks in Dorico. One of the reasons I switched to Dorico!
Another reason was flat ties 
a decades long desire! Imagine my utter confusion when I found out that flat slurs are a thing (never seen those in real live!) and Dorico doesn’t support flat ties …
+1 for flat ties.
If you look closely at the Lutoslawski’s example, flat ties need a different geometry than flat slurs in Dorico. The starting and ending curve usually has a fixed length, which is not affected by the actual length of a tie. Unlike flat slurs, it’s not supposed to be proportional to the length.