Varese, Cowell, and modernism

I am quite familiar with Varese's works as many focus on wind instruments. I performed Octandre in college, but my interest in his work grew from a quasi-scientific inquiry. I was fascinated in Varese's exploration of sound and the capabilities of acoustic instruments. While Octandre was not immediately appealing on an artistic level, careful study revealed its masterful construction, beautiful sonorities, and dance-like lyricism. Although this is likely his most tuneful work, this is the piece that opened the avant-garde world to me.  This was a critical moment in my artistic development in which I realized that, if I don't like or understand a work, it might be my fault, not the composer's.
   This was my first encounter with the Poem electronique, and I was struck by how immediately I recognized Varese's voice, even though he was writing in a slightly new idiom. Secondly, I was struck by how much it sounded like Varese had exhausted the capabilities of acoustic instruments, and this was just the next step in his progression. Now, when returning to his acoustic effects, it seems like Varese had been attempting to create this electronic sounds all along in his acoustic works.
  One final note on Varese and modernism: Ionisation has always seemed to be his most accessible piece, but I have struggled to figure out why. There is none of the melody, lyricism, or rhythmic clarity available in his other works. I think the work owes much of its success to its manipulation of our preconceptions of what music needs to sound like. We don't expect any of the aforementioned qualities in a work for percussion, so when we notice thematic recurrence and development on top of a general notice that this is a good, well-constructed piece, we are extra delighted; but in Varese's works for non-percussion instruments, we are immediately put off that the work doesn't sound like what we think it should; this initial judgement is very hard to discard, even when we notice melody, lyricism, and masterful construction.

As a pianist, I have been familiar with Cowell's The Banshee, but this was my first experience with The Tiger. What a powerfully descriptive work! It is very easy to see the tiger ruthlessly stalking its prey, the chase, the kill. Beyond this work as a simple illustration, Cowell creates the impression of power and instinct. Moreover, the work is well constructed and interesting musically throughout because of Cowell's exploration of color and motivic progression.
  Listening on Youtube, I was also struck by how much a simple visual aid, even one completely abstract, aided my musical comprehension:

Cowell's Quartet Romantic is indeed romantic as each voice explores a different tempo, constantly changing. This must be extremely difficult and tedious to perform. While listening, I noticed how even this challenging avant garde work changes texture and color exactly when the listener is ready for a new idea. He's a good composer.