[Eric Westfall]

Thank you for the response. I'll downgrade my OS to Yosemite, read the 'Help us help you,' (presently busy putting out other fires) -- yes, it's a 21.5" iMac. Sorry for the typo. I don't have the computer in front of me, it's at my studio. The Pro Tools soft I am using is 12.4. I will beef up to 16 Gig Ram. I don't know what's meant by 'dedicated audio drive.' The sessions are on the desktop, and no external drives are involved, nor am I using any audio interface. Just the Mac Built-in output.

As for what *exactly* happens, while using Pro Tools, working on a mix of a song that was recorded at 96K, 5, 10 or 20 minutes go by, and suddenly I hear very loud static/crackling, and then, in addition, loud beeps, three in succession, then three more, then three more, as the computer freezes. (It's really loud!) I go for the option-command-delete keys, the computer shuts down and then restarts. No error messages.

Yes, I have a lot of reading to do.

Thank you, sincerely, for the input.