Q: Mac Sierra Audio break up

Well, it is a release candidate, but probably close to the final version.

Also, don't forget Spotlight takes a very long time to map the drive and Journaling takes some time to Index.

If you open Activity Monitor do you see any process using a -lot- of CPU.

Also... you didn't say if you were using a dedicated Audio Interface, if so, does it use drivers, have the drivers been certified for Sierra, are you using the latest drivers?

Did you upgrade while leaving the interface plugged in, if so unplug the interface from the computer, reboot the computer and let it settle before plugging the AI back in.