Japanese magazine "Otona no Kagaku" (Science for Adults) volume 17 has what appears to be a lengthy article on the theremin featuring Eri. It also includes a kit to build a miniature desktop theremin you can actually play! Check out videos of Masami Takeuchi rocking a demo and Lydia Kavina playing "What Child Is This?".
Dying to try it for yourself? You can buy the issue on eBay for about $30 USD.