A palimpsest is a manuscript page from which the text has been scraped or washed off so that the page can be reused for another document. Often, there are traces visible of previous writings.
With the term 'choralimpsest', I mean a new composition (chorale prelude) which bears visible traces of existing materials, like a collage.
Here, I use material from chorale preludes by Dietrich Buxtehude (cantus firmus) and Georg Böhm (pedal line).