From then on his activity as a drummer extended to playing in orchestras. As a vibraphone and marimba player he started to compose and perform “zappaesque” music. Later he studied drumset with Robert Hinze at the Hochschule für Musik und Theater Hamburg and completed both an Orchestra's and an Artist's diploma. During this time he was a member of the Interpreters' and Composers’ collective “Hinz- und Kunst” and contributed to some of the ensemble’s community compositions.
All rock music activities ceased, rather he premiered a lot of contemporary music works (of H.W. Henze, N.A. Huber etc.). At the same time his first theatre music and film scores came into being. In addition travels took him to Africa, to get to know the culture of the Maasai and Samburu tribes (with whom he sporadically lived). Due to the fact that what he experienced there was so different from the so called European advanced culture, 20 years had to pass, until his African experiences manifested in his work. After the Artist’s diploma and the Hinz und Kunst’s breakup Kaul performed as street musician for some time and he together with the flutist Astrid Schmeling and the guitarist Michael Schröder founded the Ensemble L’ART POUR L’ART, which he dedicated many of his compositions to and with which he traveled the world giving concerts. A stronger conversion to composing started during the last years of the last millenium due to the collaboration with the composer and improviser Malcolm Goldstein. Goldstein advised Kaul to further dedicate himself to composing. He worked with composers and artists as John Zorn, David Moss, Elliott Sharp, Carla Bley, Mauricio Kagel, Hans Werner Henze, Vinko Globokar, Hans Joachim Hespos, Alvin Lucier, and others and as a drummer and composer toured Europe, North and South America, Japan, Korea, Taiwan, India and Canada. CDs with his compositions were released by Wergo, HAT HUT and nurnichtnur, among others. He obtained composition contracts with German broadcasting organizations such as DLF, HR, WDR, SR, of the Opera Houses in Hamburg, Hannover, Berlin and Munich; of Ensembles like one to one, L’ART POUR L’ART, Schola Heidelberg, Lucilin, Nomos Quartett, of festivals like the Wittener Tage für neue Kammermusik, the Festival+ of the Bayerische Staatsoper, Rainy day Luxemburg and of Institutions like Mutemus New York, IMDDarmstadt and the Arno Schmidt Foundation. Together with Astrid Schmeling in 1999 he founded the many times prizewinning composition master class for children L’ART POUR L’ART ("Echo Klassik" Award for „Haltbar gemacht“ in the category „Classical music for children“ (2012), Schallplattenpreis (2012), "Junge Ohren Award" (2011), Advancement award music education (2009)). The master class consists of half-year long classes with individual and group lessons for children and young people from the ages of 7 to 18 years, during which concerts take place regularly. Matthias Kaul’s works comprise instrumental music and music theatre pieces, radio plays, installations, improvising concepts. Ever since the end of his studies he has been working as a committed „freelance musician“.
Er arbeitete zusammen mit Komponisten und Interpreten wie John Zorn, David Moss, Elliott Sharp, Carla Bley, Malcolm Goldstein, Mauricio Kagel, Hans Werner Henze, Vinko Globokar, Hans Joachim Hespos, Alvin Lucier, u.a. und unternahm als Schlagzeuger und Komponist Tourneen in ganz Europa, Nord- und Südamerika, Afrika, Japan, Korea, Taiwan, Indien und Kanada.
CDs mit seinen Kompositionen erschienen bei Wergo, HAT HUT, nurnichtnur, u.a..
Er erhielt Kompositionsaufträge von Rundfunkanstalten wie dem DLF, dem HR, dem WDR, dem SR ,von den Opernhäusern in Hamburg, Hannover, Berlin und München; von Ensembles wie one two one, L‘ART POUR L‘ART, Schola Heidelberg, Lucilin, Nomos Quartett; von Festivals wie den Wittener Tagen für neue Kammermusik, dem Festival+ der Bayerischen Staatsoper, Rainy Days Luxemburg und von Institutionen wie Mutemus New York, IMDDarmstadt, und der Arno Schmidt Stiftung.
1999 gründete er gemeinsam mit Astrid Schmeling die vielfach preisgekrönte Kompositionsklasse L’ART POUR L‘ART (Förderpreis Musikvermittlung 2009, Junge Ohren Preis 2011, Klassik-Echo für „Haltbar gemacht“ in der Kategorie „Klassik für Kinder“ 2012, Jahrespreis der deutschen Schallplattenkritik für „Haltbar gemacht“ 2012) In Halbjahreskursen werden dort Kinder und Jugendliche von 7 bis 18 Jahren einzeln und in Gruppen unterrichtet, wobei regelmäßig Konzerte stattfinden.
Matthias Kauls Werke umfassen Instrumentalstücke, Musiktheaterstücke, Hörspiele, Installationen, Improvisationskonzepte. Seit Ende seines Studiums arbeitet er entschieden als „freelanced musician“.