{{#imslpmsg:addfile}} Use a pipe after addfile to separate, then put the number by which you want to increment the file number displayed; for example, {{Addfile|1}} would increase the file number displayed by 1 (i.e. one cross-referenced file in addition to the files that are there).
{{#imslpworkentry: Tod und Verklärung, Op.24 | |Symphonic Poem |Instrumental (other) |Op.24 | | | |Meinem lieben Freunde Friedrich Rösch zugeeignet. |Romantic |1891 | | }}