It turns out that part of the solution is sending the host mode to the ATOM. My code above did not do that (thus none of the commands were working.)
Not knowing the full state machine of the ATOM QR, I somehow assumed host and continuous were opposite modes - but I was mistaken.
I'm still unclear on how to send the Setup Code Prompt that is shown in the QR code.
So I have a version that makes no sounds - but I'm unclear if it was totally from the Serial2.write calls, and not from the scanning of that Setup Code Prompt mentioned
here
thanks,