Analytical discussions of music often make use of structures such as trees and graphs, which are generally presented in graphic form aligned with a score. The best know examples are the reduction trees in the style of Lerdahl and Jackendoff, but there are many others also. Only a few have well defined representation schemes, and even fewer have a means of making explicit the alignment between elements in a score and elements in the analytical structure. In this paper we propose an XML schema, interoperable with MEI, to overcome the problems of the multiplicity of representations currently in use, and so facilitate the sharing of data and its representation together with music notation using standard tools.