 As a composer, Schlee has written works in all forms, which have been published by Bärenreiter, Lemoine, Leduc, Universal Edition, Doblinger etc.He got commissions among others from Gesellschaft der Musikfreunde Vienna, Vienna Konzerthausgesellschaft, Süddeutscher Rundfunk (SDR), Camerata Salzburg, Ensemble 20.Jahrhundert, Wiener Musiksommer, Mürztaler Werkstatt, Upper Austrian Stiftskonzerte, Mariahilf-Kultur Graz, Cappella Nova Graz, Copenhagen Philharmonic, Göttingen Symphony Orchestra, Württembergische Philharmonie Reutlingen, International Beethovenfeste Bonn, International Organ Week Nürnberg, Siemens Arts Program, Guardini Foundation Berlin, Theater an der Wien Vienna, University of Music Graz, kunsthaus muerz, Ensemble die reihe, Bachfest Salzburg 2008, Southwest German Philharmonic Konstanz, Staatsorchester Stuttgart, Deutsche Staatsphilharmonie Rheinland Pfalz, Gewandhaus zu Leipzig, International Barocktage Melk, and Musiktage Mondsee.