[Woodduck]

I disagree strongly with the idea that Wagner was more of a symphonist than an opera composer. He was by nature a dramatic composer - "dramatic" in the specific sense - and not a symphonist. His harmonic language, orchestral virtuosity, and way of structuring music developed as they did specifically for the purpose of illuminating dramatic action and meaning. No one has ever been more gifted at finding vivid and precise musical equivalents for specific feelings, ideas, atmospheres, even objects, or at tracing musically the emotional trajectory of extended sequences of dramatic events. It was his innovative techniques of composition, born of drama, that led some musicians such as Tchaikovsky to misunderstand him - there are still people who don't "get" what he was doing - and attempts by subsequent composers to incorporate his musical ideas into the forms of absolute music were fraught with difficulties and pitfalls. Wagner himself was well aware of the problems; as he contemplated those symphonies he never got to write, he remarked that "in the symphony one thinks very differently," and he warned young composers against trying to plunder his work for "effects" which he had created for dramatic, not symphonic, purposes.

 

[Woodduck]

Berlioz and Liszt. Even if he wrote purely instrumental music, I suspect Wagner would have still based his symphonies on a dramatic narrative the way that Berlioz and Liszt did. This would enable Wagner to use his system of leitmotifs to pattern the work. It's hard to imagine Wagner writing in a more conventional symphonic idiom after famously declaring the form to be dead after Beethoven's 9th.

He left one clue, or at least one hint, as to his intentions. He said something to Liszt about a "new" symphonic form based on the metamorphosis of themes. That suggests a further development of the Lisztian symphonic poem, and also suggests Sibelius to me. Evidently he didn't have traditional sonata form in mind.