Baas studied at the Manhattan School of Music in New York with Dave Liebman and Phil Markowitz and at the Conservatory of Amsterdam, where he graduated in 2010 with a Masters.
In 2010 he founded The More Socially Relevant Jazz Music Ensemble with saxophonists Ben van Gelder and Maarten Hogenhuis, bassist Sean Fasciani and drummer Mark Schilders, which according to De Volkskrant was “the hippest and most exciting jazz band in the Netherlands in 2012”.
He has performed at the North Sea Jazz Festival and other festivals in the Netherlands. He also toured with the Ben Bryden quartet through Great Britain, with Bright Noise through Belgium and with Ramón Valle through South America. He also performed with Mona Lisa Overdrive and as a guest soloist with the Dutch Youth Jazz Orchestra and the New Rotterdam Jazz Orchestra. In 2015 he performed his jazz opera Discombobulatrix for the first time at the North Sea Jazz Festival.
Baas teaches at the Codarts Conservatory in Rotterdam.
Baas received the Deloitte Jazz Award in 2010. In 2013 he won the Edison Jazz National with his album Mostly Improvised Instrumental Indie Music. In 2017 his album Discombobulatrix also received this award. In 2017 he was composer in residence at the Alto Adige Jazz Festival in South Tyrol.