In the first system here Dorico did what I wanted: it turned the long tones into big fat notes without ties. But in the second system I get this really busy, distracting chain of tied half notes. I don’t know what I did to get it right the first time and wrong the second time. Any advice?
From bar 616 it’s not unmetered, you’ve entered a (implicit) 4/4.
What if you select the signpost and delete it?
Or make it an explicit open meter
I don’t know what you mean by any of that. In both instances I just deleted bar lines. I want an unmetered section of music here. I don’t want all the ties. What is a signpost? Do you mean the red rectangle that says “4/4 (q,1+1+1+1)”? If I delete that all the barlines reappear. What is an explicit and implicit open meter and how to I make an explicit open meter? I thought all I had to do was delete the barlines….
It didn’t show in the first photo, but the text in the red rectangle is the same in both systems.
Create an open time signature (shift-M open) at the start, then delete the barlines. Otherwise Dorico will just be creating a pickup bar that is very long.
Aha! That works. thanks!

