A similar problem with sonata – allegro form occurs when combined with pandiatonicism. Without functional harmony, no tension is achieved through tonal wandering. Thus the exposition tonic to dominant 'modulation" would be meaningless in this context. Furthermore, the development must rely on other techniques to build tension. Usually, both pandiatonic and atonal symphonies have used dense counterpoint and an increase in dissonance to build tension in development and homophony and more 'perfect" or 'modal" intervals to relieve it. Anton Webern uses a form in the first movement of his opus 21 symphony, which is an example of this progressive conception of the sonata allegro form. The pandiatonic and synthetic scale symphonies of Ellen Taaffe Zwilich and freely atonal 3rd and 4th Symphonies of Roger Sessions also exhibit examples of this approach. .

             The practice of continuous variation popular in many twentieth century musical idioms conflicts with the idea of a recapitulation in sonata – allegro form. Again, this convention in the twentieth century is not without precedent. The practices of thematic transformation, Idee Fixe" and organic development, while different in aesthetic conception, have the common result of creating a musical thought (melody, harmony or timbre) that is subjected to variation in novel ways throughout a piece, without a need for repetition of the original form of the melody to give a piece a feeling of 'closure." These reappearing ideas were often used as themes in a varied form in the beginnings of other movements in the symphony, sometimes eschewing all relation to classical symphonic form, such as with Richard Strauss, in favor of the variation of a theme that would represent a concept. The second Viennese School and later many other composers of the twentieth century adopted this practice with the organic writing evidenced in Brahms and molded it into the modern practice of continuous variation, which creates another barrier, from the music theorist"s standpoint, between the modernist and classicist in the writing of symphonies.