While at UBC, she co-founded the Trio sTREga, consisting of clarinet, cello and piano, in conjunction with her fellow DMA students at UBC. Over the time the group changed its profile and nowadays exists as a clarinet-violin-piano ensemble.
As a soloist Katarzyna Marczak has appeared at festivals and music seminars. In 1992 she performed as a pianist in the finals of the Competition of Contemporary Music in Warsaw. In 2003 she recorded a number of contemporary pieces for clarinet, released in 2005 on CDs accompanying scores published by the Polish Music Edition (PWM). In 2008 she succesfully premiered the famous HARLEKIN by Karlheinz Stockhausen, a 45-minute long stage dance piece for solo clarinet. She presented the piece already on a concert tour in Poland in November 2008, as well as in The Banff Centre for the Arts, during her creative residency in Fall/Winter 2008/2009. In 2012 Ms. Marczak returned to Poland and founded CMM "Gaia", the Centre of Music and Music Therapy, which focuses on early childhood music education, and music as a relaxing medium available for everyone.