Born in 1947 in Warsaw, he studied sound engineering and composition with Tadeusz Baird, Andrzej Dobrowolski and Włodzimierz Kotoński at the Fryderyk Chopin State High School of Music (now the Fryderyk Chopin University) in Warsaw. He taught composition, orchestration, interactive improvisation, electronic and computer music at the Fryderyk Chopin University of Music, the Bacewicz University of Music in Łódź, and the Krzysztof Penderecki Academy of Music in Cracow, as well as moderating contemporary music workshops for jazz musicians and sound engineers. In 2012 Bronisław Komorowski, President of Poland, awarded him the state title of professor. He cooperated with the Polish Radio Experimental Studio (from 1973) and worked at the Center for the Creative and Performing Arts at the State University of New York at Buffalo. 

Knittel has composed orchestral, choral and chamber music, operas and ballets, performed numerous electroacoustic and computer works, and created sound installations. His discography comprises more than 60 albums. He has given performances throughout Europe as well as in Asia and the Americas. Concerts dedicated exclusively to his music have been held in Brazil, Czechia, Spain, Germany, Russia, the United States, and Hungary. He served as director of the Warsaw Autumn Festival (1995–98), president of the Polish Composers’ Union (1999–2003), president of the Polish Music Council (2005–17), as well as member of the Board of the European Music Council (2014–18). In 2006 he founded the Ad Libitum International Festival of Improvised Music. In 2003–6 he was a member of TVP’s (Polish state television) Supervisory Board, in 2004–10 – member of the Programme Board of the Zachęta National Gallery of Art, in 2006–22 – member of Society of Authors ZAiKS. As a musical journalist, Knittel has contributed to such magazines as Tygodnik Literacki, Ruch Muzyczny, Studio music magazine, as well as TVP’s classical music department and PegazTV programme.

His accolades include the Solidarity Award for Music (1985), Polish Composers’ Union Award and Cyprian Norwid Prize (2003), the Gloria Artis Silver Medal of Merit to Culture (2005), the Gold Medal for Guardians of National Remembrance Sites (from the hands of Władysław Bartoszewski, 2005), and the Medal of the KEN National Education Committee. In 1998 he received a grant from the Foundation for Contemporary Performance Arts in New York, and in 2017 the Gustav Mahler Composition Prize and the Theatre Award of the City of Gdańsk for his opera The Last Judgement. 

Knittel was a cofounder and member of several improvised music ensembles, including KEW Composers’ Group (with Elżbieta Sikora and Wojciech Michniewski, 1973–75), Cytula Tyfun da Bamba Orkiester (with Andrzej Bieżan, Mieczysław Litwiński, and Tadeusz Sudnik, 1981), the Independent Electroacoustic Music Studio (with Paweł Szymański, Stanisław Krupowicz, Andrzej Mitan, and others, 1982–84), the interdisciplinary group Freight Train (with Piotr Bikont, Marek Chołoniewski, and Włodzimierz Kiniorski, 1986–2017), the European Improvisation Orchestra (1996–98), CH&K&K Trio (with Chołoniewski and Kiniorski, since 1999), and Mud Cavaliers (with Jerzy Kornowicz, Ryszard Latecki, Tadeusz Wielecki, and others, since 2003). 

Selected works (since 2000): Out of the Depths Have I Cried unto Thee, O Lord... to psalm texts (2000), Spielverkehrte Reise for soprano, actor, and electronic sounds, to words by Piotr Bikont (2000), Sonatas da camera nos. 8–20 for various performers (2000–16), Weather Reports, performance with Krzysztof Zarębski and Zofia Knittel (2000), El maale rahamim... for mixed choir and symphony orchestra (2001), Norwid Songs for soprano and piano (2001), Negev II for voice, percussion, and electronics (2002), Der Zirkus ist gekommen for soprano, female dancer, flute, cello, piano, prepared piano and electronics (2003), V2R Trio for clarinet, violin, piano, and electronics (2003), To Touch a Snake From the Inside, touch-and-sound installation (2003), The Passion of Our Lord according to St Matthew for voices, mixed choir, two percussion players, string orchestra, and electronics (2004), A Memoir from the Warsaw Uprising for five actors, female choir, piano, cello, symphony orchestra, and electronics to words by Miron Białoszewski (2004), Concerto for Harpsichord and Orchestra (2004), ...in the opposite direction..., electroacoustic music (2004), Social / Anti-Social, performance and video installation (2005), electronic waves (2005), Vagante for soloists, orchestra, and tape (2005), Toccata for symphony orchestra (2007), Cheap Imitations, chamber music for flute, clarinet, piano, string quartet, and tape (2008), Snatches of Memory II for two pianos, electronics, and video (2007), The Four Seasons, sound installation (2008), Chopin Air, sound installation (2010), free for Windows for guitar and electronics (2011), Meetings (in Two Unfinished Acts), music for Polish Dance Theatre and Grand Theatre in Łódź (2011), free for(m) macwin nos. 1–3, electroacoustic music (2011–18), What Is Not for electronics and chamber ensemble (2012), Partita 1 (Koori) for saxophone, symphony orchestra, and electronic media (2013), Partita II (Inuit) for flute, string orchestra, and electronic media (2013), AD-W2014 for actor, improvising soloists, orchestra and choir (2014), Like They Were Not Here, or a Rebellion at Królikarnia, sound installation (2015), The Last Judgement, an opera to a libretto by Mirosław Bujko (2017), Like a Stone for improvising soloists and choir (2017), Oneg Szabat for flute, violin, cello, amateur choir, video, and electronic media (2019), Canticum profugorum, oratorio for voices, solo instruments, choir, children’s choir, orchestra, an electronics to words by Tadeusz Sławek (2020, rev. 2022), Interludes 1&2&3 for six solo voices (2020), Ballad of the Murdered One... for soprano to words by Wisława Szymborska (2021), Voices for four actors, chamber choir, chamber orchestra, and electronics to words by Jan Polkowski (2021), Concert at Przyczółek Grochowski (2021), insects _ birds _ animals, vocal piece for children (2021), Maurycy Beniowski. An Alternative Children to words by Maciej Wojtyszko (2022), untitled_003-023, untitled_024-044, electroacoustic music (2022), It’s just a feedback, electroacoustic music (2023), 17°C 2023.07.03 for cello and electronics (2023), 5,298 record for 21 instruments and electronics (2023), Gdańsk Nostalgia for carillon (2024).