Here is a clip from HarmoniCollege 2018 of Michael Rubin and Clint Hoover demonstrating playing 12 keys with one harp. I had heard of it being done, but had never heard it in person. It was an astounding performance. Clint Hoover will offer private lessons at HarmoniCollege 2019
You can read more about HarmoniCollege 2019 with instructor Mike Caldwell at www.hhcwv.com