The title isn't meant to be translated into French

"Pas seul" is a dance term - it refers to a solo for one dancer, usually for the prima/primo, instead of for two, like a pas de deux. If you've ever seen The Nutcracker or Swan Lake, you've seen two of the most famous pas seuls in ballet - The Dance of the Sugar Plum Fairy and The Dying Swan. A clavier is similar to a harpsichord or piano. So in effect, the title is "Solo on Clavier" or "Solo on Piano". It's referring to the solo dance and to the one arm the mc will use to compose the piece. It's actually a very clever play on words.