I don't think Opus Clavicembalisticum is the hardest piece ever?
Or at least, it's major difficulty just lies in its duration but not on the rhythmical, speed, accurary and musicality difficult
In fact I don't believe at all (despite their -often senseless- blackness) that most difficoult piano works belong to the avant-garde and 12-note-row period
In fact it's very easy to chear with these pieces as you don't need such accuracy in musicality, tone or even in hitting the right notes for a simple anatomical reason meaning when our ear can distinguish clear musicality and when it becomes unimportant
Instead of random notes, impossibly wide chords and crazy rhythmic notation (21/16 + 24/16 + 21/8 + 7/2 : 16 for example) what really is difficolout is playing with a perfect tone a musicality especially when the piece is fast and the rhythm is complex
Anyone would be able to create difficoult pieces by making the score full of blackness, even a 3 years old boy would be able to do this with a music notation program and random notes (in fact not only many avant-garde composition where written by writing down what the child of the composer plumped on the keyboard rondamly but also some avant-composer even wrote impossible pieces, and they were proud of it, impossible because they defeated any mathematical rules for measure filling)
I guess that Mozart, Tchaikovsky, Sinding, Clementi, Chopin, Debussy and all the others would have been able to create such complex pieces just by filling the page with complex chords and fast quintuplets, but they didn't do it because it would have been a joke to them to create complexity in such a unelegant manner
I know a composer that showed me that he can create a dissonant, avant-garde super complex piece in just 1 hour using the telephone guide numbers as a hint for his row
But only when he put musicality and avoid strange effects for the sake of it it may requires three months to him to write a good piece but the result is more balanced and not just a show-off of fake complexity
The most difficoult thing in music is create complexity while being simple, that what many composers of the past tried to do with hard work
They knew it would have been easy to just throw in a lot of complex devices into the music but they never tried it because they were proud of themselves only when difficolouty was not self-evident or created with dirty tricks, their pieces had to be complex yet simple to the hear, complex rhythmically and musically yet even in the score
For that reasons (a lot of past avant-garde composers are nowadays for the first time admitting the lack of musical ideas compared to the amount of phylosophycal ideas of modernism and their tricks to try to appear brilliant or intellectual) I don't think real complex pieces are to be searched in this period but on the understimated scores of the impressionism and neorilism period
It's like cheating when cooking
You can create a recipe in few minutes just by mixing in a bowl all the strangest ingredients in the world like quinoa, wild fennel, a condor egg, emu milk, norwegian raspberries, canistel, guarana and it would look like something exotic, innovative and hard to prepare/cook; but it would just be a fake innovation, a fake exocitism and a fake difficoult, it would just be a dishonest mess where for the sake to appear complicated and hard you just mix things randomly without caring for balance, flavours harmony, right cooking time
Or on the other hand you can create an elaborated and complex apple-pie without using the dirty trick of putting a lot of strange ingredients to appear brilliant and serious but with a perfect accuracy in your semplicity, matching the various aromas and flavours, trying to find the right ingredients even if they're few or not exotic
It, despite the first recipe looking more complicated and hard to prapare the second one is more hardest because you can conceal your talent or lack of talent in a lot of different random ingredients, you have few ingredients and you have to mix them perfectly to create something palatable and innovative
It's very easy to appear intellectual, brilliant, serious, profound, complicated and difficoult but everything is just fake obtained through the easy way and that's why composers of the past avoided this path at all cost preferring few ingredients, few special shocking effects but a lot of balance and musicality and nothing where to hide the ignorance or lack of talent in
I know a composer who wrote a good string quartet in 1969 with lot of effort and love and it took him 9 months. The theather didn't accepted it saying it was
too easy and uncomplex so he instead wrote a string quartet just by putting all the strange effects in it randomly, wide chords, rhythm change every two measure, strange dynamics mark like "fluting on the keyboard" "xilophoning on the cello" , put a lot of dissonances in it and wide quinteplets and sixtuplets plus screams from the chorus plus random trills, wide jumps and several climax in the strangest moments
It took 3 days to complete that work
He said to me it meant nothing to him, he didn't put love in it, it didn't put his talent in it it was just a work as the avant-garde theaters wanted it to be
The piece was this time accepted and played by a not-so-happy orchestra
He said to me eventually that the strangest thing is that his first piece who took him 9 months was really rhytmically and musical complex just apparently simple but it was not accepted because condired too easy or not complex, and yet the second work that was easy as a piece of cake to compose just by putting all the tricks used to have the piece look like complex was really nothing complex and nothing hard, no musicality, no rhythm
No, (he conduct orchestra) he considers Beethoven harder than Busoni or Berg and always tells to me that the difficoulty in playing the piano is not playing pieces like a Berlioz Sonata but playing Mozart well
Food for thought...
P.S
If it were shorter, OC wouldn't be harder than many other pieces out there, it's the harderst piece, just the longest
Daniel