If your problem is with Aria compatibility, would your message be better (also) posted on the Garritan Forum?

The general rule that I follow is, don't upgrade your OS if your software isn't compatible. There are times when someone's computer dies, and they replace it. You're forced into using a new OS in this situation. This is just a fact of life when living in a computer age.  It's no one's fault really. If nothing else works for you, have you tried using the instruments that came with Logic?

I have always said that no one should upgrade anything on a Mac unless they have to because of Apples' backward-compatibility attitude. On this occasion, I broke my own rule. There was no warning issued about this incompatibility.

Re: the Logic Instruments, there are no baritone horn, euphonium or Eb trumpet instruments (the ones I need) in the standard set and suitable sounds can't be obtained via EQ.

>On this occasion, I broke my own rule...<

If you were properly backed up, you can restore High Sierra. If you have a Time Machine backup that predates your Mojave install, it’s easy and just takes a few hours—if not, it’s a time consuming pain but still quite doable. Post those questions on macrumors.com and there are those who will post the procedure. Since it is not a Finale or Garritan issue, no reason to do that here.

As to Apple’s so-called backward compatibility attitude, there is none. Apple moves forward and expects the world to catch up. They’re very upfront about this.

Thanks Mike, I thought that might be a route. Re: Apple, I'm an 80-year-old pensioner and I can barely afford to breath most days, and Microsoft manage to keep up to speed without abandoning customers so ruthlessly, JM.