As a student, he made his debut in J. Strauss’s Die Fledermaus singing the part of Prince Orlofsky at the Castle Opera in Szczecin and in Monteverdi’s La Coronation of Poppea in the role of Nero at the Collegium Nobilium Theatre in Warsaw. He also performed at the National Philharmonic in Warsaw, the Szczecin Philharmonic, the Baltic Philharmonic in Gdańsk, the Silesian Opera in Bytom, the Polish Theatre in Warsaw, the Grand Theatre-National Opera in Warsaw, the Grand Theatre in Łódź, the Royal Castle in Warsaw, the Opera Nova in Bydgoszcz, the National Forum of Music in Wrocław, the NOSPR Concert Hall in Katowice, the Witold Lutosławski Concert Studio in Warsaw. He also performed on international opera stages and festivals, including: in Italy (La Biennale di Venezia), Japan (Tokyo Bunka Kaikan), Estonia (Saaremaa Opera Festival), Strasbourg (Festival Musica) as well as in Germany, Belgium, Kazakhstan, China, Serbia and South Africa.
His concert repertoire includes numerous works from baroque to contemporary music. His opera repertoire includes, a.o. such works as „Dido and Aeneas” by H. Purcell (The Witch), „Julius Caesar” by G.F. Handel (Sextus), „Die Fledermaus” by J. Strauss (Prince Orlofsky), „La Coronation of Poppea” by C.Monteverdi (Nero), „Rinaldo” by G.F. Handel (Rinaldo), „Agrippina” by G.F. Handel (Nero), „Orpheus ed Euridice” by Ch.W. Gluck (Angel) „The Marriage of Figaro” by Mozart (Cherubino), „Romeo and Juliet” Ch. Gounod (Stephano)  „Lost Higway” by O. Neuwirth (Andy), „Miracle Unfinished” by S. Kupczak (Jesus), „Man from Manufaktura” by R. Janiak (Horse/Sailor) „Only the sound Remains” by K.Saariaho (Spirit) „Paradise Lost” by K. Penderecki (Raphael, Death).
He collaborates with outstanding Polish composers. Performed a.o.: „Shakespeare’s Sonnets” by Paweł Mykietyn (in Rome – Corso Polonia/X Edizione del Festival delle Arti Unite, in Malta -Teatru Manoel/Concert of Polish Contemporary Music Masters, in Fribourg -Post Fine Arts, in Lviv -XVII International Contemporary Music Festival, in South Africa -National Arts Festival 2015, in Poznań -Festival “Nostalgia” 2017),  Fake Opera by Wojciech Błażejczyk (Warsaw – Autumn Festival 2021),  Voyager by Sławomir Kupczak (Grand Theatre National Opera in Warsaw) Rafał Ryterski (Warsaw Autumn Festival 2022). He also made a CD recording of Agata Zubel’s opera “Oresteja” (recorded by Polish Radio).
 
Michał Sławecki performed with Baroque Collegium 1685 several times, presenting solo parts from the  “Saul” and “Messiah” Oratorio by G.F. Handel.
 
Photo: artist’s archive