I am struggling to see Schubert and Tchaikovsky as mostly joyful. Schubert is one of the most melancholy composers, I think, although I am skeptical about the alleged remark of his that he didn't know any happy? joyful music. Sure, as with Tchaikovsky that aspect might have been exaggerated in reception and the latter has a lot of festive music to balance the gloom of the "Pathetique" and others.
Well, yes, I agree that Schubert is essentially a melancholy guy. But...
Firstly, there is melancholy and melancholy. His is not of the gloomy, hopeless and despairing kind, but a gentle, mild, bittersweet one. Not a cloudy, cold, and snowy mid-winter late evening (
Winterreise notwithstanding) but a warm, glowing and beautiful Indian summer sunset.
Secondly, for all his melancholy, to my ears his music sounds mostly joyful (admittedly, this may have possibly got something to do with his infallible melodic gift). The only work of his which has no joy whatsoever, no ray of hope at all, no moment of relief is
Winterreise. All others juxtapose sorrow and joy in the most natural manner, and in the end the lighter mood generally prevails.
Pretty much the same applies to Tchaikovsky as well, melodic gift included, the difference being that he has no completely doom-and-gloom work (at least none known to me). Even the Pathetique has that charming waltz.
Overall, I'd say that judging by the works I've heard (not all of them but a susbtantial part and certainly all of the important ones), both Schubert and Tchaikovsky wrote more joyful, or cheerful, at least bittersweet, than sorrowful music. And yes, their reception tended to obscure this fact.
To me they are maybe the most bipolar composers? I agree with you that Schubert immediately makes me think of melancholy, and of course Tchaikovsky is famously moody...but then there are things like Schubert's symphonies 2/3/6 and Tchaikovsky's orchestral suites and ballets. Not too many people spent so much time working at both extremes of the emotional spectrum.
These are good points. But why do you single out Schubert's symphonies 2/3/6? There's not a single one of all others, not even the Tragic, not even the Unfinished (the second movement strikes me as rather cheerful), which does not have joyful moments interspersed with sorrowful ones. As for Tchaikovsky, there's much more joyful music to him than just the ballets and the suites: all the concertos, the Serenade for String, the Capriccio Italien, Snegurochka, most of the piano music fits the bill. Heck, even
Manfred has that delightful pastoral movement.
Now that I think of it, Chopin is not very gloomy either. The PCs and other works for piano and orchestra, mazurkas, waltzes, some of the preludes, polonaises, scherzos, ballades, impromptus and nocturnes, the barcarolle, the bolero and the juvenilia are quite cheerful, actually --- either completely or partially.