16G RAM is not enough for many Kontakt libraries along with other apps. The way to test this is to try a single library in Kontakt that doesn't require as much overhead. You can use the Activity Monitor to monitor your results. On my 4-core iMac, it took 32G for my apps to have enough breathing room.

Three things to do:

1) Reboot daily. Many apps have memory leaks and a reboot clears physical RAM. 

2) Browsers and web sites are the worst offenders for being RAM hogs. Turn off your browser when running Finale and Kontakt. Even better, turn off your browser and reboot first.

3) Run sudo purge in Terminal.app. Not as effective as a reboot for clearing RAM but better than doing nothing. All sudo commands require your admin password before running. The only thing this command does is to purge physical RAM of temporary storage not being used by active apps — doesn't do a great job but it often helps.

With most apps including Digital Performer, opening separate instances of Kontakt Player optimizes your cores—6 instances will optimize your distribution since you have a 6-core processor and you should assign your instruments accordingly.

I can't vouch for Finale—there are so many complaints about Kontakt in the app that I'm not interested in taking the time to test it. I do know how it works in other applications.

With 16G RAM, you will likely be running sudo purge a lot.

In Terminal, if you use the up arrow, this will recall the last command you ran. Hit the up arrow till sudo purge appears, hit Enter or Return, enter your Admin password, Enter or Return again, you're done. The process takes a second or two—perhaps three on my iMac that is a lot slower and has twice as much RAM.

Since upgrading to 32G RAM, I almost never run the command unless I forget to boot that day. I rarely boot on Saturday so I can give you real world examples using TechTool Pro 9 to measure available RAM. My iMac has been on 27 hours since the last reboot, only Google Chrome is running.

Start — Available RAM: 10.79G

After sudo purge — Available RAM:  19.73G

After reboot before starting Chrome — Available RAM: 29.38G

After reboot with Chrome up — Available RAM: 24.11G

Thanks so much Mike!

I'd be happy to upgrade my RAM, but want to make sure that's really the fix. The thing that concerns me is that I have no trouble with Kontakt and Finale on my older computer 8Gigs of RAM - it is FINALE 2012 though. Would that be consistent with RAM being the issue?

  Thanks so much!

David

I agree: don't start throwing money at the problem until you have a better idea what the problem is. If you reboot and keep your browser off and the problem goes away or lessens, RAM is a probable culprit. Also, learn to create multiple instances of Kontakt Player—one per instrument up to 6, the number of cores you have. More than 6 has no benefit to you. See what happens.

The place to start is the Activity Monitor. That will show you what's going on and what VIs are CPU hogs.  

Run Console to see if anything is trying to load that shouldn't. In 2013, I had a major problem when HP drivers and Finale 2009 Help files were trying to load when I called up a certain app ... what the ?!?!? Anyway, I removed those files and solved that problem. Sometimes, you just don't know till you go looking.

Run sudo purge now and then to see if it helps. If it does, you need more RAM.

I do think that, for most of us, 16G is not enough RAM anymore. I feel sorry for those with laptops and notebooks who cannot install more. My iMac tops out at 32G but that seems to be working for me—20G, however, caused my system to choke now and then.

You can install even more. There's an issue with yours, EEC Unregistered (max 32G) vs EEC Registered (max 128G) RAM cannot be mixed. Even though the initial cost is more expensive, I'd start with a pair of 16G EEC Registered sticks. This puts you at 32G and, if you need more later, you will still have 2 slots free that you can fill one at a time. 

There are many vendors besides OWC but they have great info:

https://eshop.macsales.com/shop/memory/Mac-Pro-Memory#1866-memory

When I load instruments into Kontakt, there's a display at the top of the screen, just left of my Bluetooth icon. That display shows exactly how much ram is being used by the samples I load.  My Macbook Pro is maxed out at 16 GBs of ram, but I rarely have issues because of insufficient  RAM.

 I don't know if it makes a difference, but I just use Kontakt with Logic, and use GPO with Finale.