Simplify the following text for a Grade 9 native English-speaking person.
Original: After being sent on a lengthy tour of Europe starting 1927 â `` including London , Paris and towns in Germany â `` during which he demonstrated his invention to full audiences , Theremin found his way to the United States , arriving December 30 , 1927 with his first wife Katia .
Simplified: Theremin moved to the United States , arriving December 30 , 1927 with his first wife , Katia Constantinova .