One striking example of mid-nineteenth century is the last movement of Chopin's Piano Sonata N.2 in B-flat Minor Op.28.
Ligeti calls this piece ``...probably the first atonal piece of in the history of music''1.2
Although there is a clear harmonic structure which appears in the quasi-arpeggio evolution of the identical lines of both hands, the speed of harmonic changes and their intently chromatic profiles actually makes the ``feeling'' of tonality to weaken to a considerable degree.
The perception of such a music is more ``global'' rather than detailed (structural). The popular epithet ``winds blowing through graves...'' actually gives a rather poetic yet accurate description of how this music was (is) perceived.
Beside being called ``the first atonal piece'' by Ligeti, the Chopin example above brings us to the very important question of sheer musical speed and perception.
Mehmet Okonsar 2011-03-14