By Nathan B. Lawrence, Lawrence University

Classical music seems to have a reputation for being straight-laced, stuffy, and obsessed with rules. But over the centuries, hundreds of composers have tested the boundaries of musical expression in strange and unique ways. Here are ten prime examples.

1. 4'33" — John Cage

In the last 50-odd years, John Cage's personal favorite work, 4'33" has become something of a running joke and subject of derision in the music world. It's easy to see why: to perform the piece, a pianist walks on stage, opens the lid of a grand piano, sits down at it, and then lowers the lid. With a stopwatch set for exactly four minutes and thirty-three seconds, he sits in complete silence, occasionally opening and closing the keyboard to indicate the various "movements" of the piece. What kind of music is that?!

When Cage wrote 4'33", he seems to have intended for us to turn our attention not to the music on stage, but to the music and sound we all make as we watch this performance. In the seemingly silent concert hall, a symphony of new noises start to emerge that we took for granted moments ago: coughs, the squeaking of your seat as you slightly move, and even the guy scratching his head 30 feet away become a part of this score.

2. Organ2/ASLSP (As SLow aS Possible) — John Cage

In 1985, John Cage continued his tradition of questioning the nature of music and performance with ASLSP (As SLow aS Possible), a piece which—as the title suggests—simply instructs the performer to play it "as slow as possible." In 1987, Cage published a new version for organ and since 2001, a cathedral in Halberstadt, Germany has been making good on Cage's instructions: Their organ has been playing the piece so slowly that it is not expected to finish until some time in the year 2640. In October 2013, more than a thousand people gathered to hear the thirteenth note change in the piece; another one is not expected to occur until September, 2020.

3. Fugue in G Minor (Cat Fugue) — Domenico Scarlatti

Though this piece may seem tame by today's contemporary standards, the (potentially apocryphal) story of how Baroque composer Scarlatti supposedly came across the rather unconventional motif makes it worth mentioning on any list of weird classical pieces. Scarlatti claimed that his cat, Pulcinella, was prone to walking across the keyboard. One day, in one of the feline's unexpected performances, the melody now synonymous with the "Cat Fugue" caught the musician's attention, and the rest was history.

4. Duetto Buffo di Due Gatti — Unknown

On another cat-related note, this 1800s art song also seems worthy of the "weird" crown, this time because of its unorthodox lyrics and musical humor. Duetto Buffo di Due Gatti, which roughly translates to "humorous duet for two cats," seems to tell the story of two cats meeting, lashing out at each other, and eventually making friends in an operatically styled duet using only the word "meow" (spelled "miau" in most scores). Though the work was originally published unattributed, conventional wisdom seems to point to Barber of Seville composer Gioachino Rossini as either the composer or a target of the work's parody due to its heavy appropriation of the famous vocal writer's compositional idioms.

5. Einstein on the Beach — Philip Glass

Let's zip forward 150 years to another "operatic" work. In 1975, Philip Glass, perhaps the most famous composer from the school of minimalism—which attempts to uncover the beauty in repetition and slight variation—wrote Einstein on the Beach, an opera in four acts and by far one of his longest works.

We call Einstein on the Beach an opera largely because we have no better name for what it is. There isn't much traditional opera in the work: there is no plot; the singers seem to represent specific thematic threads more than characters; and seemingly orthodox structural and performance vocabulary like "scene" and "aria" seem to take on a different meaning. Perhaps the most interesting parts of the work are its "Knee Plays," connecting tissue between the acts that combine a chant-like choral pattern with highly rhythmic human narration for an ethereal effect. The unexpected moments of synchronicity between the two parts create a strangely paradoxical feeling of serene disorientation.

6. Violin Concerto No. 2: The American Four Seasons — Philip Glass

Another from Glass's minimalist library, this piece was composed as a companion to noted violinist Robert McDuffie's touring performance of Vivaldi's Four Seasons concerto. Aside from the piece's unorthodox instrumentation—which puts a synthesizer and harpsichord on the same stage—Glass does something else to surprise us by refusing to reveal which movement goes with which season, forcing you to "figure that one out for yourself."

7. The Unanswered Question — Charles Ives

Though the first drafts of the piece appeared in 1908—more than 50 years before the first pangs of minimalism would emerge—the effects of Charles Ives's The Unanswered Question can be felt throughout the movement. The piece features three different ensembles: strings, brass, and flutes, all separated from each other and playing in wildly different rhythms and keys. The score also calls for the string section to be hidden from the audience, creating an eerie, disembodied sound.

8. Requiem — Andrew Lloyd Webber

Perhaps the strangest part of this piece isn't the bombastic and unapologetic dissonance or rock-influenced orchestration, but the composer himself. Webber, who is far more famous for his musical theatre works like Jesus Christ Superstar, Cats, and The Phantom of the Opera, has said he wrote the requiem as a personal contemplation on mortality and legacy after the death of his father. Despite the hard rock sound, Webber seems to have successfully captured the more tender feelings of grief and loss, especially in the softer moments of his "Dies Irae" movement.

9. String Quartet No. 6 — Brian Ferneyhough

Any of Ferneyhough's pieces would have been at home on this list: The composer has a highly unorthodox style that includes unusual time signatures, and he routinely pushes instruments to the limits, forcing the use of unorthodox techniques to create unexpectedly harsh sounds. In fact, Ferneyhough is frequently regarded as one of the most difficult composers to play on any instrument.

10. A Musical Joke (K. 522) — Wolfgang Amadeus Mozart

While many composers on this list attempted to use unorthodox techniques and stylistic choices to depict complex emotions or uncover human truths, Mozart did it simply to entertain! His Musical Joke was a piece written intentionally to be as bad as possible. Mozart disobeyed many harmonic rules of the time, created cloyingly repetitive patterns, and even intentionally wrote parts that would sound like the musicians were playing wrong notes.