Firstly, let's look at some of the situations being talked about:
- Collaborative Works — written by different authors acting together (e.g. 4_Improvisations, by Taneyev, Rachmaninoff, Arensky and Glazunov);
- Interopolations — additional music written by one composer which was intended to be inserted into an existing work by another composer (e.g. Carl Binder's Overture to Offenbach's Orpheus in the Underworld;
- Completions — works which were left unfinished by their composer, and which were completed posthumously by another (e.g. many of Mussorgsky's compositions.
- Editorial works — works by one composer that were edited for publication by another (the most common category).
- Arrangements and Transcriptions — versions of works by one composer made later by another, such as piano reductions, vocal scores, or rescoring for different instruments (again, there are many such examples).
- Potpourris, Fantasias, Variations — works by one composer that were based on themes by another, and which don't preserve the form of the earlier work. The majority of Renaud de Vilbac's output would fall into this category, as would works such as Benjamin Britten's ''Young Person's Guide to the Orchestra'' (after themes by Purcell), which isn't yet P.D.
- Translations — books or vocal librettos rendered into one language from another.
- Writings — books or articles by one person about the life or works of another composer.
Aside from collaborative works (which are relatively few), the rest of the arrangements, etc., are currently being dealt with in two different ways:
- they are all placed on the page for the original composer
- they are placed on the page for the second composer, with cross-references from the pages for the original work
- the files are listed under both composers' pages
- nothing appears on the second composer's page to indicate their contribution to a work by another composer
- cross-references between work pages can appear untidy, and are particularly difficult to use in the case of editors and translators (who may not qualify to have their own pages in the "composer category".
- having the same file listed twice in different locations makes it difficult to keep track if changes are made to the original file or its descriptions, and is generally considered to be bad programming practice.
- creating new pages such as "List of arrangements by Johannes Brahms" or "List of editorial works by Franz Liszr", and linking these to the relevant composer's homepage under the "See also" heading. In fact the Liszt example already exists — see http://imslp.org/wiki/Category:Liszt%2C_Franz
- creating sub-categories along the lines of "Arrangements by xxxx" and "Editorial works by xxxx", which would then automatically appear in a separate section of the composer page (above the main listing). The sub-categories for the second composer would have to be added to the work page for the first, with new sub-category pages created. So this could become a little complex, but it is probably workable.
- creating new composer categories for collaborative works, e.g. 4 Improvisations (Taneyev, Sergei/Rachmaninoff, Sergei/Arensky, Anton/Glazunov, Alexander). This would only work effectively in a limited number of situations, and even then it could prove a little unwieldy.
- different categories could be created for composers, editors, arrangers, translators, etc., using different layouts and colour schemes to show the difference. But some provision would have to be made for one person falling into multiple categories.
- the layout of the current composer pages could be changed to produce separate lists of works composed by them, works arranged by them, works edited by them, and so on. This is likely to require more complex programming than the other options mentioned so far.