I can see what you mean, but i too would advise using the chamber music section. The reason why there is a sub-section for solo keyboard music is that due to its polylinear abilities, the majority of music written for keyboard instruments is unaccompanied. Works for monophonic instruments tend to feature a keyboard accompaniment which it would seem most appropriate to describe as forming a chamber ensemble. Coupled with the fact that, unlike the solo piano, in the concert performance tradition it is rare for a recital not to contain at least some duo repertoire, it would therefore seem appropriate to include unaccompanied works for these instruments in the same chamber music category.