I'm not familiar with Schumann. Googling music theory forums indicates he's respected today mainly for his compositions for piano, while his symphonies are held in low regard. I'm now listening to his piano concerto in A minor, finished in 1845. I'm not very familiar with the 1830s or 1840s, but it doesn't sound anything like music from the 1820s or earlier.

I don't think music like this could have been written before Schumann. The piano necessary to play it didn't exist. Some key moments in the development of the piano:

• 1820: first 7-octave piano
• 1820-1843: various patents on the iron piano frame
• 1820: the vertical escapement, allowing one to play the same note twice in succession
• 1834: steel wire, probably made possible by iron frames, allowing louder playing and hence greater dynamic range
• 1840: stronger steel wire
• 1844: the sustain pedal invented

The music forums say Liszt and Ravel's works required the double escapement, and some say Chopin's did, while one argues Chopin's pianos didn't have it. No word on Schumann.