Hi,
I found a German source with an article by Termen in the table of contents of the "Funkamateur" journal.
L. S. Termen "Elektronik und Musik"
Funkamateur
Nr. 4, 5, 1970 Pages 161, 213
(Heading) "Elektroakustik und NF-Technik" L. S. Termen Elektronik und Musik (electro acustics and low frequency techniques)
(Heading) "Geschichtliches"
(to the history, electronics and music)
(Termen is the Russian name of Theremin)
Source: FA-Inhalt_67-06, Jahrgangs-CD 2006 Funkamateur (yearly CD of the Funkamateur journal, 2006, table of contents of old volumes)
May be, the article is available in libraries.
Best regards
Bernd
(I do not know whether such topics are appreciated, but I think, it is on topic and not known.)