Jan Krejča plays theorbo, baroque guitar and renaissance lute. As a sought-after basso continuo player, he collaborates with many top local and foreign ensembles (Collegium 1704, Collegium Marianum, Ensemble Inégal, Musica Florea, Czech Ensemble Baroque, Capella Cracoviensis, Capella Anna, Les Traversee Baroque, For Several Friends, etc.) and soloists Jana Semerádová, Hana Blažíková, Tomáš Král, Sergio Azzolini, Judith Pacquier, Lenka Torgersen, Daniel Deuter, Anna Fusek, Magdalena Kožená, etc.
He regularly performs at festivals such as Prague Spring, Prague Autumn, Concentus Moraviae, St. Wenceslas Celebrations, Haydn Lukavice, Summer Festival of Early Music. He performs on Czech Radio and Czech Television and performs on dozens of recordings for Accent, Arta records, Supraphon, Rosa, etc. He has released his own solo album of virtuoso Italian music for the theory of Intavolatura di Tiorba. He is a lecturer of historical plucked string instruments at the Academy of Early Music at Masaryk University in Brno.