Great questions and thoughts - thank you very much.

The house is 63 years old.  Yes, the "Open Ground" duplex outlet was identified with a three prong plug-in outlet tester, before I opened it up.  Inside there are only two sets of two wires for the two outlets; the wires are cloth and rubber covered.  There is no ground wire   The outlets are three prong so presumably were added after the original wiring. 

Other room outlets test as "Grounded," hence my idea to first use one of these outlets and move my audio equipment, furniture, carpets, under lay et al around(!)

Longer term I'm considering having an electrician install a dedicated 20A branch circuit and/or a GFCI duplex outlet...thank you all again for all your kind help.  It is much appreciated.  Enjoy your music! 

So this would work for protection on a two wire outlet? Thoughts...Thanks 

Panamax MD2 2 Outlet Direct Plug In Surge - White

Thank you for the helpful additional insights, thoughts and recommendations.

Good news!  The home's current main panel was put in about 5 - 10 years ago. The home's prior owner is a builder.  He lived here 22 years and was renovating all over, up to a few months before he sold in 2023.  

Today I'll get a Husky GFCI plug-in adapter for the Open Ground outlet, to add some safety, if not protection against surges...Next I'll look in to an electrician installing a dedicated power circuit for the audio equipment and/or doing a full home re-wiring as needed...thank you.