Born in 1981, he graduated from the composition class of Zygmunt Krauze and the sound engineering class of Andrzej Lupa at the Fryderyk Chopin University of Music in Warsaw as well as in journalism and political science from the University of Warsaw. He is the director of the Fryderyk Chopin University’s Computer Music Studio and a member of the Creative Group that develops Warsaw’s Hashtag Lab – Contemporary Music Space. His works have been performed by ensembles and orchestras such as Klangforum Wien, Musikfabrik, the Polish Radio Orchestra, United Instruments of Lucilin (Luxembourg), Gorzów Philharmonic, New Music Concerts Ensemble, Wratislavia Chamber Orchestra, Kwartludium, and Hashtag Ensemble. 

He has won prizes in several competitions for composers, including the International Confederation of Electroacoustic Music Prix CIME for #NetworkMusic (2019), the 1st Krzysztof Penderecki International Composers’ Competition ARBORETUM (3rd prize, 2012), and the 52nd Tadeusz Baird Competition for Young Composers (1st prize, 2011). His Warsaw Music reached the finals of the European Broadcasting Union’s Palma Ars Acustica in 2016. In 2013 he took part in IRCAM Forum Workshops in Paris, and in 2017 – in the Composer Collider programme with the Musikfabrik ensemble, which resulted in the composition of String Theory for 11 Harry Partch string instruments. Four albums dedicated to his music have been released: Music of Strings (Chopin University Press, 2022, Fryderyk Award for Contemporary Music Album of the Year), General Theory of Relativity (2021, KAIROS), Thrash Music (Requiem Records, 2018), and Loopovisations (2013, For Tune). There are also many CDs of improvised music performed with Hashtag Ensemble and The Intuition Orchestra. Błażejczyk writes acoustic and electroacoustic music, works for the theatre and film. In his compositions, he uses instruments that he builds himself: objectophones (musical instruments constructed out of everyday objects, whose sound is transformed live), the gesturophone (an electronic device controlled by gestures), as well as atypical string instruments. 

An active concert guitarist, he plays new music on the electric guitar and with live electronics. He is a member of Hashtag Ensemble and has performed improvised music with ensembles such as Mud Cavaliers and Electronisches Glück, artists such as Adam Pierończyk, Agata Zubel, Krzysztof Knittel, and Joëlle Léandre. As a sound engineer, he specialises in new music concert recording and sound projection as well as film sound design. He also holds workshops for children on electroacoustic music and the use of sound objects. 

Selected works (since 2013): LoPassHiCut for double bass and live electronics (2013), Guitar Sculptures for electric guitar and live electronics (2013), Bethlehem for choir, soprano, baritone, duduk, percussion, organ and electronics (2013), A Concise History of the Death of Jean Calas for baritone, choir and symphony orchestra (2014), Trash Music for ensemble, voice and objectophones (2014), Particle Horizon for electric guitar, bass guitar, objectophones and live electronics (2014), Warsaw Music for instrumental ensemble, voice and live electronics (2015), Music of Strings for electric guitar, piano and string trio (2015), Concerto for electric guitar and string orchestra (2016), Spirits of the Dead for flute, violin and viola (2016), DATA Selfie for three performers and electronics (2017), Angels of Peace for oboe, clarinet, horn and double bass (2017), #NetworkMusic for voice, chamber ensemble and electronics (2017), String Theory for 11 Harry Partch string instruments (2017), Concerto for viola, clarinet, electronics and string orchestra (2018), Étude semi-concrète. Study for Many Strokes on Different Objects for electric guitar, objectophones and electronics (2019), Gesturophony for gesturophone (2019), Aether for flute, clarinet, trumpet, violin, cello, double bass and electronics (2020), Shine for actor, chamber ensemble and electronics (2020), Stringphonies, a cycle for untypical string instruments (2020–22), Co-Relations for voice and gesturophone (2021), The Bunker. Fake Opera for four performers, chamber ensemble and electronics (2020–21), The Science of Destruction for electric guitar (2022), Postquartet for string quartet (2022), Liturgy of the Object for symphony orchestra, choir and objectophones (2023), 1-Day Challenge for three performers and electronics (2024), The Basilisk, the Witch and the Band, electronic miniature (2024).