The Museum of Music in Paris possesses a collection of 280 instruments from the twentieth century. Most of them belong to the general families of electric and electronic musical instruments, which we will call ‘electrophones', in deference to the name chosen by Curt Sachs. From the onset, it was decided to start the collection with the Ondes Martenot. Our aim was to define a model approach that could also be applied to other electric and electronic instruments. This work involves organising the instruments, studying them in order to outline conditions of appropriate conservation, and determining which kind(s) of restoration should be undertaken.