Though Hirschfeld-Mack is often credited with the invention of the Bauhaus color organ, German scholar Ingo Petzke has recently argued that Schwerdtfeger developed a similar device–the Reflecting Color Light Play–first, and that he and Hirschfeld-Mack were not only collaborators but also rivals. Petzke points to the first Bauhaus book, covering projects between 1919 and 1922, in which two pictures of Schwerdtfeger’s instrument appear (it had its debut in Kandinsky’s home in 1921) before Hirschfeld-Mack had created his own version. Largely ignored by the history constructed later, an embittered Schwerdtfeger wrote in a 1964 letter that:

“a couple of weeks before the Bauhaus Week, Hirschfeld-Mack grouped with some Bauhaus students and developed his play. I was refused access to these. Rehearsals went very secretively. At a ball during the Bauhaus Week the group premiered their version. The involvement of several people made it more complex than mine. That’s when I left the Bauhaus because I felt deceived.”