Richard Wagner

Wagner wrote his own librettos and spent most of his life on a handful of long operas. That scale changed how he wrote: instead of separate numbers with applause between them, the music runs continuously, and the joins are made by the orchestra rather than by the singers.

His main tool is the leitmotif, a short musical idea tied to a person, an object or a feeling. The ideas come back transformed, so the orchestra can tell the listener something the characters have not said yet. In the concert preludes, where there are no singers, the motifs carry the whole argument.

Harmonically he delays. A chord that sounds like it must resolve one way resolves somewhere else, or not at all, and the ear is kept waiting. Tristan is the extreme case: the piece opens with an unresolved chord and the same withholding runs through it. Later composers took this as a starting point, which is why Wagner turns up in the history of almost everything written after him.