Beethoven's works without opus number Most composers who "directed" the opus numbers of their works also left a number of compositions without opus number. In Beethoven's case, the list of his works would be a very different thing without these Werke ohne opuszahl (WoO); it would, in fact, be less than half as long. The summary by Georg Kinsky and Hans Halm includes 138 works with opus number and no fewer than 205 without. The latter category is a real garden of delights, and there is no reason at all to regard it with suspicion. We must, after all, remember that Beethoven's most popular piano piece, the album leaf Für Elise, is included in this group (WoO 59). There are various reasons why a composer like Beethoven might decide to let one of his musical offspring lead a life without an opus number. He might find a work too unimportant to give it an official place among symphonies, string quartets, and other large-scale compositions. And sometimes there was no reason to include it in the cataloguing process: Beethoven, for example, wrote several pieces of chamber music for members of his circle of friends which were never intended for performance outside this private world.