In Essential Cowell: Selected Writings on Music by Henry Cowell 1921-1964, Cowell describes his friendship with Carl Ruggles and calls him "irascible, lovable, honest, sturdy, original, slow-working, deeply emotional, self-assured, and intelligent." As an example, he tells how it was important for Ruggles to rank composers by historical importance and they spent many hours debating if Tchaikovsky was thirteenth or fourteenth. He also, not surprisingly, praises Ruggles for his mastery of dissonance.
Cowell also does a short analysis of Ruggles' Organum and points out how the melody line does not repeat the same note too soon, how despite the composer's tendencies the final chord must be less dissonant if not consonant, and how an example of dissonant counterpoint works.
He finishes by suggesting that Ruggles is in a similar position to Anton Webern, in having written a small number of short, dense works, albeit with more melodic flow.