My intuition is that there can be only a limited number of basic formal ideas which are clearly perceptible and make sense to a listener. These can be varied, stretched, and combined in an immense variety of ways, but certain patterns need to be present if the progress of the music is not to seem random or chaotic. It wouldn't be surprising if all the possible basic formal principles have already been discovered, though I suppose that's going to depend partly on what we consider "basic."

Composers through the ages have used such basic structures as verse-and-refrain (ABAB), "bar" form (AAB), more complex alternations (ABCABC, etc.) including rondo (ABACADA), "bow" form (ABA), cantus firmus, theme-and-variation, continuous or progressive variation, and various combinations and inflections of these. Sonata form was, I think, the structural idea of the greatest power and potential within the Western tonal tradition, which stood composers in good stead for as long as tonality remained strong enough to make it meaningful. I'm not sure any comparably fertile idea has come along since.

 

What I'd like to exist would be a form without (or with very little) literal repetition, but also some kind of "rules"/expectations how the piece will progress and develop/vary its themes, non-repetitive but still rather predictable.

 

Doesn't sound terribly unlike some existing music. But when you say "a form" do you really mean a specific form or just a principle of development? Fugue, for example, is really a principle rather than a form; it has procedures but no predetermined overall structure. And which elements of the music do you want to avoid too much repetition? Would that apply to metre and rhythmic figures and harmonic progressions as well as themes? Certain late 19th- and early 20th-century symphonic movements and tone poems seem to strive for a sense of organic logic without too much literal repetition: Sibelius, Nielsen, Mahler? We might even say that complete acts of Wagner operas - say, act 3 of Tristan - meet your criteria pretty well. But the larger the form the harder it would be to get a sense of unity or inevitability without repetion.

 

There's certainly music with sense of organic logic and without much literal repetition like lots of tone poems, but these are basically rhapsodic and do not conform to any specific form. I wouldn't apply the avoidance of repetition to metre, rhythmic figures or harmonic progressions necessarily, but basically the music progressing constantly rather than going back, but with certain formula on how it will progress. I guess the rather free treatment of sonata-allegro form by the late romantics comes closest.

 

I'd say that the practice of continual variation used by the 2nd Viennese school is a unique form that evolved specifically in the 20th century. Serialism applied this practice to all components of music in the second half of the century. Of course, you could argue that Wagner used this technique to some extent long before Schoenberg, but in his case it was used much more loosely and in the context of much larger forms.

But most 20th century music can be traced in some way to old 18th century forms. Nothing is completely new.

 

I think that electroacoustic music during the 20th century was a pretty radical break from the older forms... the use of new technologies to explore new territory with unabated fearlessness of the unknown.

 

I would contend that all art (thus, music) has "form", because form (structure, shape, presence, mass) is imposed on the elements of art to create a work. Even aleatory works have form -- randomness, which serves as the form chosen by the composer.

A fantasy, such as a Liszt tone poem, is a form, too. Even if no particular segment of the music repeats (as it will in, say, sonata-allegro form or the rondo) there is present a form, but one that dispels of repetition.

Minimalist music, that very repetitive stuff such as Steve Reich writes, also has form. Though seemingly homogenic, there are audible differences in the fabric of the sound from beginning through middle to end. Even the fact that we can talk about a beginning, middle, and end implies that a form is involved.

Ambient music, such as new age electronic noodlings, is sometimes described as "formless". Yet, "formless" music itself is a form, again, a form or structure imparted to the music via the composer's decision making.

Intriguingly enough, John Cage's 4'33" is a work with form. Not only is it in three distinct movements, it is "formed" or structured or shaped by time.

If a composer could surely achieve a musical work "without form", it would prove an earthshaking advancement in the arts certain to rank with the invention of the wheel.

 

I'd like to hear a piece with a palindromic structure (i.e. A-B-C-D-C-B-A) but without exact repetition (i.e A-B-C-D-C1-B1-A1). The recap could be a retrograde, or retrograde inversion of the expository themes. It doesn't have to be limited to 4 themes (5 or 6 or ....) Does anyone know of a piece like this?

 

A composer named Charles Knox wrote several pieces he called Semordnilap, but I've never analyzed the structure.

The one in my collection is just piano, no bellyach-- I mean singing.