Originally written for clarinet and bassoon, these duets were believed to have been published in Paris.  There is some debate on whether or not Beethoven wrote them, but they were published in his lifetime and there is no record or letter of him either confirming or denying the duos.  The third duo is the most unusual, though it is written in the sonata-form.  The secondary key area does not offer a real thematic passage, while the recapitulation is like exposition only at its very beginning and end.