When he took the position at the restored church, destroyed by bombing in World War II, with a new Kern organ, he programmed a first recital with music by Bach, Brahms, Reger, Louis Vierne and his own.

[1][3] He took master classes with Marie-Claire Alain, Hans Fagius, Lorenzo Ghielmi, Olivier Latry and Jean-Claude Zehnder.

[3] In 1998 Kummer was appointed a Lutheran district church musician (Bezirkskantor [de]) in Kirchheim unter Teck.

[6] In 2005, Kummer was appointed the organist at the Frauenkirche in Dresden, when the church was reopened after the completion of its restoration from destruction in World War II.

[1] From 2007, Kummer was also a dozent for organ repertoire, liturgical performance and improvisation at the Hochschule für Kirchenmusik Dresden [de].

[7][10] Music journalist Claus Fischer of the MDR commented at the time that Kummer was perhaps more an artist than an organiser, and thus not ideally suited to the position.

According to his family, he collapsed at Dresden Main Station on his way to teaching in Würzburg,[4][7] where he had been appointed to a summer position at the Hochschule für Musik.

[12] A reviewer wrote:Kummer takes great care, as the music progresses and the registrations become more imposing, to maintain clarity at all times in the contrapuntal lines.