L'idée is often mistaken for being the first movie to use the Ondes Martenot musical instrument. In fact, it is the second. L'idée was made in 1932 but the soundtrack was added in 1934, a few months after the release of the movie Liliom. Liliom had a score composed by Franz Waxman which used the Theremin. Therefore, L'idée is the oldest movie to use the Ondes Martenot, but not the first one.