Back in Poznań, an inspired Kaczmarek and his friend, Grzegorz Banaszak, would write and play music in campus toilets – praising their acoustics and resemblance to the candlelit confinement Kaczmarek experienced in Grotowski’s laboratory. Dubbing their duo (later trio) the Orchestra of the Eighth Day (Orkiestra Ósmego Dnia), they began by accompanying the performances of the legendary Poznań theatre group from which they took their name, eventually moving on to independent road tours abroad. When Kaczmarek got a scholarship to the United States in 1989, little did he know he was leaving Poland for good.
Barely able to pay his rent, and sustaining his wife and four children on gold cards, J.A.P. kept up appearances in his new home of Los Angeles drinking cocktails with millionaires while wondering how many days he had left before bankruptcy. Slowly but surely, propositions - first in the theatre, then the film industry - began to roll in. Music for the films Unfaithful, Dreamer, Lost Souls, Washington Square, The Visitor, Get Low and a number of Agnieszka Holland pictures make up his portfolio. With over 70 film scores under his baton and an Oscar for the score of Finding Neverland on the mantle of his L.A. home, Kaczmarek finally found his way back to Poznań in 2006 for the premiere of 'Oratorium 1956' – a composition commemorating the bloody Poznań Uprising of 1956. In 2011 he founded the Transatlantyk Festival in Poz, however the annual film festival has since moved to Łódź. In 2015, he was awarded the Knight's Cross - Poland's highest military and civilian honour - for his outstanding artistic achievements and his contributions to promoting Polish culture abroad.
A little trivia: Kaczmarek is the only musician known for using an unusual instrument which is actually a self-revamped Fischer’s fidola (a type of zither).