Attached are graphic representations of Dorico memory usage in Mac OS X Catalina. I have 16GB memory. All peaks in graphics correspond with Dorico usage. I use the same machine for various other tasks daily, including Zoom, video creation, and video editing. Dorico is by far the most demanding application of memory in my workflow.
Are you sure that’s memory usage and not CPU? It seems very weird that Dorico would suddenly use all your memory and then release it.
That’s a third-party utility. What does Activity Monitor show for Memory Pressure? Have you noticed any issues as a result of high memory pressure – e.g. slow downs, freezes?
Here’s my Activity Monitor: Dorico uses a fairly consistent amount of memory. The Memory pressure graph is green and low, showing that memory pressure is light.
I’m not a Mac user, but a graph showing “memory usage” as a percentage of something doesn’t make a lot of sense, which suggests it’s actually a graph of something different.
If it is the CPU, there is an issue with the video aspect - you can search for it. A quick fix/experiment: open a file, click on the video icon to open the video window; close the window, then proceed. Your CPU usage will drop dramatically.
If it is a memory issue, then disregard the preceding.
Are you working on particularly large orchestral scores with large sound libraries? I could see the latter having a notable impact on the ram load.
FWIW, I have an old mac mini (2014) at work with 16gb ram. I never have problems (apart from playback buffering which is more a limitation of the old, weak CPU than the ram).
Further still, I have an (almost as) old imac at home with 32gb ram, and I can run Hauptwerk (very large VST with pipe organ sample libraries that can take up to 148gb+! of ram depending on the sampleset) and run a sampleset that takes 28gb ram and run it in parallel with Dorico no problem. So that’s 28gb to HW, leaving only 4gb ram for the operating system and Dorico. All within 32gb.
Also, have you tried opening a project that has the playback template set to “silent” to see if that makes a difference? I guarantee you that heavy ram load (if the utility is even measuring the pressure correctly) isn’t from Dorico itself.
Thanks to all who weighed in on this. It appears to be an odd bug with the way Dorico interacts with iStat Menus, the app I use to display system information in my menu bar. When I quit Dorico, the graphs displayed show that my memory usage never goes up over 25% in each of the 24-hour, 7-day, and 30-day graphs, but when Dorico is running, that information is displayed as going up to 100% usage. And yes, the graphs are displaying information about memory usage, not CPU. It’s an odd one, alright. In audition to this post, I’ll report it to the developer of iStatMenus.
The great thing about apps like iStat, Little Snitch, etc, is that they provide you with lots of data for you to spend time researching and worrying about, 99.9% of which is entirely normal behaviour that you can safely ignore. 
I use istat as well and don’t have any odd reports. Dorico is open right now and was open yesterday. I am, however, on 10.14.6 for OSX which could be a factor. You’re likely on a later build than me.
Edit: I should mention that the active memory usage chart doesn’t change much either. The pic is the “pressure” chart. I opened and closed a project in Dorico five minutes apart within the last 10 minutes. You can see barely any change in the second pic.
Perhaps if they used some standard terminology instead of inventing things like “pressure”, “wired”, “compressed,” etc, people would be able to understand what the charts meant.
(I’ve been worrying about computer memory usage, on and off, for about 50 years on a wide variety of operating systems, and I have no idea what those terms are supposed to mean.)
Memory Management in MacOS is much more sophisticated than “filling up a jug with water”. It tries to use as much RAM as it needs to; but it will use data compression to compress the least important resources. (Hardware compression is still faster than swapping.) Memory pressure is an indication of how much compression is being used.
Wired Memory is stuff that can never be swapped out: VM buffer caches, IO memory, etc.
Let the OS manage the memory, and if a problem manifests itself, then investigate with the OS-bundled utility. There’s no need in using third-party apps so you can keep an eye on it all the time yourself. Having Humans continually check that computers are working properly is pretty much the opposite of why we have computers.
Thanks Ben. So it’s just a new set of names for some 30-year-old concepts, then 
Thanks for checking this. Yes, I’m on 10.15.5. I’ll run it by the iStatMenus developer.
My concern about this was that I thought it might be related to some interface slowness that I experience. Open and Save dialogs react very slowly on my brand new machine in Dorico. Just trying to pinpoint the cause, and I thought there might be a memory leak that is causing interface lag.
I’m afraid it’s not unusual for the Open and Save dialogs to be a bit slow to respond; I believe this is somehow related to the new security model in Catalina. I experience a slight delay after the Open or Save dialog appears and I try to navigate to another folder not only in Dorico but in other applications as well.
Thanks, Daniel. Glad it’s not just me.