Liszt is, of course, seated at the piano and the two figures immediately behind him, leaning towards one another, are the composers Berlioz and Rossini. The bust sitting on the piano that Liszt is gazing at is Beethoven who still looms over music. One of the most important precedents for the romantic trance in music is found in the Cavatina movement from Beethoven's String Quartet, op 130. Here is that movement:
The crucial moment comes 3:57 into the movement when a new texture begins with triplet E flats in the three lower instruments. When the first violin enters a moment later with a new melody it is not in triplets so it is at odds rhythmically with the others. Beethoven marks this "Beklemmt", meaning "suppressed" or "agonized". But the most interesting thing for our purposes is that while the movement is in E flat, this passage is in the flat submediant, C flat. Those E flats in the accompaniment are the third of a C flat harmony. The flat submediant, or in less technical language, a triad built on the flattened sixth note of the scale, will be the romantic harmony par excellence, the harmony that signals the trance-state, the descending beneath the surface of feeling.
Schubert extended this technique with his Impromptu in E flat, op 90, no 2:
Like the Beethoven example, this is also in E flat major. But Schubert goes Beethoven one better: instead of just going to the flat submediant (C flat major), Schubert goes instead to the minor flat submediant, C flat minor. But to avoid writing an immense number of flats, he notates it instead as B minor, the enharmonic equivalent. (Two notes or harmonies are said to be "enharmonically equivalent" when the notations result in the same sound. For example, C flat and B have the same sound even though they are written differently. It is the same thing as writing the word 'fish' with 'ph' instead of 'f': 'phish'.) In the Impromptu the move to B minor, prepared with a G flat harmony, equivalent to F sharp, occurs at the 1:16 mark. Another characteristic romantic harmony that Schubert uses is at the 0:23 mark when he moves from E flat major to E flat minor.
This piece, like most heard during Schubert's short lifetime, was performed at Viennese salon concerts called, in honor of Schubert, "Schubertiads".