- Their popularity with the classical music-buying public (as determined by the number of recordings of their music offered for sale by Amazon.com--Mozart leads with 13,540, followed by Bach and Beethoven, and then there's a big leap down to Schubert, Brahms, Verdi, and Tchaikovsky, all with 6000-7000 recordings.)
- Versus their prominence in scholarly histories and encyclopedias of music, as tabulated by Charles Murray in Human Accomplishment (Mozart and Beethoven are tied for most eminent, followed by Bach and Wagner).
Counting the number of recordings on sale at Amazon seems like a reasonable metric of marketplace popularity, although at the Mozart v. Beethoven battle of the titans level, Mozart probably has an advantage because he wrote more music than Beethoven (e.g., 41 symphonies v. 9). If you are an obscure musician, you might try to pick up a few bucks from Mozart completists by recording an obscure Mozart piece. So, number of recordings on sale doesn't necessarily match up to sales. But, it seems likely to be good enough.
As you can see, overall, scholars and classical CD-buyers don't disagree all that much. Still, the scholars value early composers (pre-Vivaldi) more than the public. Vivaldi, Bach, and Handel were standing on the shoulders of giants; it's unfair that the public doesn't enjoy the music of their great predecessors as much, but that's just the way it is.
The other main area of disagreement between Amazon's and Murray's rankings is over 20th Century composers, especially atonal ones such as Schoenberg, Webern and Berg. (If you are not familiar with the music of Arnold, Anton, and Alban, this KTEL-like 1977 infomercial for a greatest hits album entitled "Beloved Hits of Arnie Schoenberg and the Second Viennese School" will get you up to speed. [Okay, this video version is even funnier.]) They were very talented at impressing scholars with the idea that they were the Next Big Thing in the History of Music, but the public has been less impressed. (It turned out that, so far, there really hasn't been a Next Big Thing. Western art music, which has been so productively changing styles for a couple of centuries, more or less ran out of gas in the 20th Century just as the cultural world became obsessed with style-changing as the mark of true greatness.)
The only two major composers from the second quarter of the 20th Century to be more popular with the public than with the scholars are Prokofiev and Shostakovitch, both of whom had to worry that if they let their compositions get too avant-garde, the middle-brow (but highly opinionated) Stalin would have them shot. So, the classical music-buying public evidently owes Stalin a debt of gratitude.
The composers who are most popular with the public relative to their importance to music historians tend to be melodic Romantics from the second half of the 19th Century and early 20th Century. The scholars rate opera composer Giacomo Puccini (Madame Butterfly) only 10% as important as Mozart, but Amazon carries 30% as many Puccini titles as Mozart titles. (Puccini's aria "Nessun Dorma" from Turandot has become a staple of television talent shows in the last few years.) Next in line is Bizet (Carmen), then Tchaikovsky (The Nutcracker), and Dvorak (The New World Symphony).
Then comes the early 18th Century Baroque composer Vivaldi (The Four Seasons). It's possible that the scholars are underrating Vivaldi's importance in music history because most of his compositions were lost from the late 18th Century until the 1920s. However, he was known to J.S. Bach, and had some influence on him.
Others more popular than their degree of scholarly eminence would suggest include Grieg, Verdi, Gounod, Saint-Saens, and Brahms (although, obviously, Verdi and Brahms are giants by any measure).
I wonder if opera fans are more likely to buy multiple versions of an opera than are symphony fans, which might account for opera composers doing well in terms of number of recordings on sale. To my untrained ear, it's easier to be a fan of a particular singer than a particular conductor or orchestras, so there might be more demand for multiple versions of operas. On the other hand, operas are expensive.
At the other end of the scale--composers more written about than played--we find, besides a lot of early composers and the late 12-tone boys, Cherubini. I had never heard of Cherubini, but Beethoven saw him as his greatest contemporary. Other big names on the Important-but-not-Popular list include Stravinsky, Berlioz, Weber, and Wagner.
Murray's methodology might overrate Berlioz's representation in music reference books because one of Murray's techniques is to look at the index and count the number of pages a composer's name appears on. Berlioz was not only a great composer (Symphonie Fantastique), but also a great music journalist. So, he gets quoted a lot about other people, which inflates the number of times his name appears in indexes relative to a composer who let his music do all the talking for him.
Evidently, the craft of composition had reached maturity in the second half of the 19th Century. By then, most of the tools to appeal to the music-literate public had been created. (Most film score music today sounds like late 19th century orchestral music, stylistically.)
After about 1900, however, the enormous richness of the 19th Century repertoire weighed down composers, driving them into experimentation, most of which has not proven enduringly popular with the CD-buying public. Strikingly, the composer universally believed by musicians to be the greatest genius of the second half of the 19th Century, Wagner, is not particularly popular these days compared to the awe with which he was regarded a century ago. Wagner got there first, and was able to create popular interest in his innovations that lasted for a few generations, but without him around to blow his own horn, public appreciation for Wagner seems to be fading relative to his Italian and Viennese rivals.
My impression is that 18th Century orchestral music has been growing in popularity at the expense of 19th Century orchestral music. We're just not profound enough anymore for the Romantics. Most pre-Beethoven stuff tends to sound like the composer introduced it with the words, "And here, your Archdukeness, is a little something to brighten your day," while post-Beethoven 19th Century music tends to sound like the composer is inviting you to "Come with me on journey to plumb the most profound depths of my infinite soul." Yeah, hey, that sounds great, but first I've got to check my, uh, Twitter account, so can I have a raincheck on the soul-plumbing?