Modern music
Modern music is that which is written in an idiom that came just after the period that any given music-lover was last able to understand.
Beethoven
Beethoven is regarded as a public company in which a number of people have shares and it is important to know how many shares each of them holds. Thus one talks of Klemperer's Beethoven, Karajan's Beethoven, Solti’s Beethoven, Bernstein's Beethoven and, after a bit of research, Furtwangler's Beethoven—those are main shareholders with Klemperer holding a working majority.
Bach
Any suggestion that you can take Bach as good clean fun can earn you a very nasty reputation. You must take Bach seriously or not at all.
Mahler
It was suddenly realized that Mahler had not written big long boring symphonies of the Brahms type which you have to listen to carefully from beginning to end in order not to miss the themes, but had, in fact, simply strung together hundreds of attractive little tunes, and it was possible to go into a coma for a lot of the symphony and still get involved when you came to again.
Bartok
Bartok is great stuff for people with the kind of mentality that takes naturally to chess and Ximenes crosswords.
