He has composed pieces for such artists as Agata Zubel – Akwaforta for female vocals, ocarinas, recorder, tape and computer (2002), Et cetera for vocals, wind instruments, string quartet and computer (2005), Andrzej Bauer – Anafora V for cello and computer (2004), Cezary Duchnowski – Akwaforta, Cikada String Quartet – Anafora VI for string quartet and computer (2005), Agnieszka Pstrokońska – Rymowanki for marimba and strings (2003), and Tech-no Orchestra – Silly Nilly for string orchestra, alto saxophone and tape (2001-2002), Palimpsest for string orchestra and tape (2002). In 2005, he composed Figliki, a piece for electronics and piano that was ordered by the Experimental Studio of the Polish Radio as part of a project entitled REJ 2005 for the 500th anniversary of Mikołaj Rej’s birthday. In 2005, he composed a piece commissioned by the Association of Polish Composers for the 60th anniversary of the Association, one of 60 pieces composed. The piece for recorder, harpsichord and electronics, entitled Kreacja I (Thinking of of Tomasz Sikorski), was premiered by The Roentgen Connection at the Musica Polonica Nova Festival in Wrocław in 2006. In 2008, the city of Wrocław commissioned a piece from Kupczak for the Wrocław Feast 2008 entitled Penultima for cello and chamber orchestra.
Apart from working as a composer, Sławomir Kupczak spends his time performing contemporary music – he plays solo and chamber performances on the violin. In 2000-2002 he was a member of the Tech-no Orchestra led by Robert Kurdybacha. In 2002-2004 he was a member of the Wrocław Theatre ZAR ran by the Centre for Research on Jerzy Grotowski's Artistic Activity, with which he carried out several performances, including Gospels of Childhood and Lazarus, in collaboration with the Butoh dancer Daisuke Yoshimoto.
He is a member of the Association of Polish Composers as well as the Polish Society for Electroacoustic Music. From 2004 to 2018, he has also taught theoretical subjects and led School Symphony Orchestra at the Stanisław Moniuszko Primary and Secondary State Music School in Jelenia Góra.
In 2015, Kupczak has been invited by the Grand Theatre in Warsaw to take part in Project P, which resulted in composing his first opera Voyager.