text: This composition unusually contains both a three-voice movement in two-stave keyboard notation and a six-voice movement written out in open score.
full_question: This composition unusually contains both a three-voice movement in two-stave keyboard notation and a six-voice movement written out in open score. This composition includes a canon with the inscription "Quaerendo invenietis" and five "Canones Diversi" followed by a "Fuga Canonica in Epidiapente." It concludes with a four-movement "Sonata sopr'il Soggetto Reale" for transverse flute, violin, and basso continuo. This composition resulted from a visit to Potsdam, where its composer was asked to improvise a three-voice fugue on a given theme, dubbed the "Thema Regium." For 10 points, name this collection of pieces by Johann Sebastian Bach based on a theme composed by Frederick the Great.
first_sentence: This composition unusually contains both a three-voice movement in two-stave keyboard notation and a six-voice movement written out in open score.
raw_answer: The Musical Offering [or Das Musikalische Opfer]