Someday I'll writeup what I'm sure will be a contentious piece about what makes Great Music, and whether there is such a thing at all. For now, I want share some brief thoughts about Scott Joplin, who was at once an extremely popular composer in his time (around the turn of the century... 19th to 20th) and remains revered as the "King of Ragtime" even today.
In academic and musicological circles, there is much hand-wringing over whether Jazz deserves to be studied as Art Music. It is undoubtedly culturally significant, as a predecessor to essentially all modern popular music, and as a unique artistic outgrowth of a democratic idealism. Whether it is "Art Music," however, is questionable. Do Jazz musicians consider carefully the artistic and aesthetic value of every note? Do they see themselves as composers, or just as musicians? On some level, these are nonsensical and unimportant questions (what matters more is the music, no?), but there is a certain scholarly significance to the why of music, and not just the what.
Before Jazz, however, there was ragtime, and while there is a fairly straightforward formalism to the rag that makes it an unlikely source of "great" music, I believe that Joplin is actually the rare Great Composer who transcends his time.
Listening to Joplin's music - and comparing it to other ragtime composers - is probably the best way to test my claim. Joplin's music is more nuanced, more melodically reflective, more groundbreaking (he wrote what we might call the first "fusion" piece in "Solace," which combined ragtime sensibilities with Latin rhythms). Joplin's mid-life visit to Europe - which spurred him to learn European harmony and counterpoint - turned him into an even better composer. A meeting with Debussy inspired the French master to try his hand at ragtime, with disastrous results, while Joplin's incorporation of European methods was seamless, enriching his later music.
Joplin even wrote two operas - one of which is lost, the other of which was not performed during his lifetime - but like many great minds, he was ahead of his time. Joplin's operas were about race at a time when that was dangerous. Joplin, indeed, was black at a time when it was almost impossible to be famous and black (famous for a good reason, anyway). And yet he was. His Maple Leaf Rag was the highest selling piece of sheet music of all time during his life, and the first to sell more than 1,000,000 copies.
Without getting into the qualities of Joplin's music - an effort too involved at this busy time to be reasonable - I'll close with this argument. In no other genre does one composer's music dominate so much. There are many famous Romantics, many Classical composers, many masters of the minuet. But in ragtime, there is only Scott Joplin. Like Bach was with the fugue, Joplin was so masterful with the rag that subsequent composers have only used aspects of it (the syncopated rhythms, for example).
Think of it this way, of the dozen or so most famous rags ever written, all were written by Scott Joplin. It's not that he was the best composer of his time, in his genre. In a very real sense, he was the only. The King of Ragtime.