The life and works of Wladyslaw Zelenski (1837-1921), a composer regarded as one of the outstanding opera composers active at the turn of the century, constitute one of the most neglected areas of research into Polish musical culture of that period. There thus seems to exist an urgent need for a new, exhaustive monograph about this composer. This is confirmed by the collections of manuscripts, previously insufficiently appreciated (PL-Wznio 4397/I, PL-Wznio 6414/I) or totally unknown in the literature of the subject (PL-Kj Przyb. 175/63, PL-Kj Przyb. 176/63, PL-Kj Przyb. 177/63) which include epistolary sources (these latter also contain documents and Zelenski's personal papers, including his Catholic baptism certificate, with the names 'Vladislaus Marianus Nicolaus'). Polish musicologists also need to examine closely the letters of Zelenski's first wife, the writer Wanda Zelenska née Grabowska (1841-1904), who actively promoted her husband's works (such as PL-Wznio 4805/I, PL-Wznio 6414/I). The article indirectly makes the case for a critical edition and publication of Zelenski's extant correspondence in full. Such an edition would need to be preceded by a thorough search not only in the Polish, but also European (and American) libraries and archives. Zelenski's letters are to be found in a variety of locations, such as the archives in Ukraine (UA-Lvs 6819/III), Lithuania (Vilnius, Lietuvos Literaturos ir Meno Archyvas, F.50.1.133), Germany (D-Bim-Doc.orig.Ladislaus Zelenski 1) and the United States (the collection of the Polish Music Center at the University of Southern California in Los Angeles). This material opens up new research perspectives. Firstly, it provides the possiblity of correcting and filling in the gaps in the chronology of the composer's development (demonstrated in the article by the example of his operatic works). Secondly, it provides an opportunity for discovering new, unknown, or little known facts (such as the composer's unsuccessful attempts, discussed in the article, to have the world premiére of his opera 'Goplana' staged in Prague and in Vienna). Thirdly, it should allow one to capture Zelenski's true creative temperament and psychological profile.