first prelude from The Well-Tempered Clavier, but at double the normal speed, with each phrase repeated interminably in a minimalist manner that parodies Glass. On top of this mind-numbing structure is added everything from jazz phrases to snoring to heavily harmonized versions of "Three Blind Mice" to the chanting of a meaningless phrase ("Coy Hotsy-Totsy," alluding to the art film Koyaanisqatsi for which Glass wrote the score). Through all these mutilations, the piece never deviates from Bach's original harmonic structure. The humor in P. D. Q. Bach music often derives from violation of audience expectations, such as repeating a tune more than the usual number of times, resolving a musical chord later than usual or not at all, unusual key changes, excessive dissonance, or sudden switches from high art to low art. Further humor is obtained by replacing parts of certain classical pieces with similar common songs, such as the opening of Brahms's Symphony No. 2 with "Beautiful Dreamer", or rewriting Tchaikovsky's 1812 Overture as the 1712 Overture with "Yankee Doodle" replacing Tchaikovsky's melody and "Pop Goes the Weasel" replacing "La Marseillaise". Compositional periods Schickele divides P. D. Q. Bach's fictional musical output into three periods: the Initial Plunge, the Soused Period, and Contrition. During the Initial Plunge, Bach wrote the for unaccompanied piano, an Echo Sonata for "two unfriendly groups of instruments", and a Gross Concerto for Divers Flutes, two Trumpets, and Strings. During the Soused (or Brown-Bag) Period, P. D. Q. Bach wrote a Concerto for Horn and Hardart (a pun on the name of a chain of automat restaurants), a Sinfonia Concertante, a Pervertimento for Bicycle, Bagpipes, and Balloons, a Serenude, a Perückenstück (literally German for "Wigpiece"), a Suite from The Civilian Barber (spoofing Rossini's The Barber of Seville), a Schleptet in E-flat major, the half-act opera The Stoned Guest (the character of "The Stone Guest" from Mozart's Don Giovanni, and the play by Pushkin), a Concerto for Piano vs. Orchestra, Erotica Variations (Beethoven's Eroica Variations), Hansel and Gretel and Ted and Alice, an opera in one unnatural act (Humperdinck's Hansel and Gretel and the 1969 film Bob & Carol & Ted & Alice), The Art of the Ground Round (Bach's The Art of Fugue), a Concerto for Bassoon vs. Orchestra, and a Grand Serenade for an Awful Lot of Winds and Percussion. During the Contrition Period, P. D. Q. Bach wrote the cantata Iphigenia in Brooklyn