Born in Warsaw in 1954, he studied the double bass performance (with Alfred Wieczorek and Andrzej Mysiński) and composition (with Włodzimierz Kotoński) at the Music Academy in Warsaw. Thanks to a Witold Lutosławski grant, he continued his compositional studies with Isang Yun in West Berlin and Klaus Huber in Freiburg i. Br. (1986-87). As a double bass player he focuses on the contemporary solo repertoire. He has performed in many European countries, Asia, and the United States.
He is also active as an improviser, playing with musical ensembles such as Mud Cavaliers and Laterna. In 1995 his A Very True Story for tape received the highest award at the EAR radio competition and Budapest, and in 1999 his Concerto à rebours for violin and orchestra (1998) was commended at the UNESCO International Rostrum of Composers in Paris. He is also active in the field of promoting contemporary music and arts education. He ran several cycles of radio programmes introducing children into the world of new music and cooperated with the Children's Arts Centre in Poznań and the Okopowa Cultural Centre in Warsaw. He was Artistic Director of World Music Days in Warsaw in 1992. In 2004 he was invited as a lecturer to the Darmstadt Summer Courses for New Music.
His works have been commissioned by institutions, festivals and ensembles such as Warsaw Autumn, Polish Radio, Poznań Philharmonic, de ereprijs, the Darmstadt Summer Courses for New Music, Klangspuren in Schwaz, Klangforum Wien, Hiroshima Symphony Association, Klangforum Wien, New Music Orchestra (OMN) in Katowice, Forbidden City Chamber Orchestra in Beijing, Plural Ensemble in Madrid, Ensemble intercontemporain, Music Workshop, Silesian Quartet, and many other ensembles and institutions.
Tadeusz Wielecki served as Director of the Warsaw Autumn International Festival of Contemporary Music between 1999 and 2016.
Selected works (since 1995): Id for orchestra (1995-96), Study of Gesture I for clarinet, piano and cello (1995), Study of Gesture II for piano (1997), Concerto à rebours for violin and orchestra (1998), Thèsis for flute (2000), Study of Gesture III for clarinet, trombone, piano, cello and double bass (2000), Credo, quia absurdum for tape and female dancer (2001), Time of Stones for chamber ensemble and amplified double bass (2002), Slabs for orchestra (2002), String Quartet (2004), The Whisper of Semi tones for double bass and chamber ensemble (2004), Schwärme for symphony orchestra (2005), Hazard and Necessity for string quartet and electronics (2006),Thee Valley of Dry Water for chamber orchestra (2007), String Vibration for harpsichord (2008), Piano Concerto (2008-9), Documentary Opera about the Round Table; new version of the documentary opera Knights of the Round Table (2009), At the beginning there was... for slammer, sampler and chamber ensemble (2009), Quartertones and HalfShades for double bass, two percussions and trumpet ad libitum (2009), Gear Wheels, Springs and Modes for violin and guitar (2010), The Thread is Spinning... IV for double bass and chamber ensemble (2012), Subjective Model. Dramatised Form for viola, tuba, tape and informal group of performers (2012), Points of Hearing for chamber ensemble (2012), The Little Shoemonger and the False King, chamber opera for children and adults (2013), Reading for orchestra (2014), Dynamistatic Composition for chamber orchestra (2015), Study of Gesture IV for string trio and percussion (2015), Wobbliness, Dynamistatic Composition II for traditional Chinese instruments (2015), Sphinx for double bass (2015), Expressions for piano and ukulele (2016-17), Multiple Image for chamber ensemble and ticking clocks (2016), Sound Pranks for sounds, gestures and mimes for children and adults (2017), I Sound Therefore I Am for two accordions (2017).