One major problem with a wiki article on this subject would be various classical-music "snobs" practically arguing with each other over the merits of certain composers, performers, conductors, etc. So realistically I don't see a wiki page happening.
With that said, here's my version of a "Classical for Beginners" primer:
The 4 main time periods (Baroque, Classical, Romantic, Modern/Contemporary) provide an easy convention: Baroque was simple, methodical, and very "mathematical". Classical became more complex-sounding, Romantic was sort of a return to passion & expressiveness, and when Modern first started out it was mostly an experiment - dissonant, atonal-type music.
There are also different types of works in classical music, as not everything is necessarily a symphony or concerto (though those two types are the most prevalent). There are also sonatas, cantatas, arias, and so forth (these words can be Googled, I won't bother with definitions). Classical music ranges from everything in between a solo piano to a full-size symphony orchestra.
I'd say the key differentiator between classical works are the time periods and composers. Some composers started in one era and lived into the next and produced some transitional work - examples of this being Vivaldi (Baroque to Classical) and Beethoven (Classical to Romantic). Each era had its own distinct style.
My advice to beginners is to seek out a time period first, and then to narrow down by composer. As I said in the other thread that was closed, today's film soundtracks have some similarities to classical music. Allow me to state some parallels here:
- Fans of epic-style music (like Lord of the Rings for example) will definitely want to start with Romantic & Modern. Specific composers that come to mind include Wagner, Mussorgsky, Mendelssohn, Tchaikovsky, Mahler, Stravinsky, Prokofiev, Dvorak, etc. There are so many more.
- Fans of intimate-style piano music will probably like Chopin (specifically his Nocturnes), Debussy, late Beethoven, Brahms, etc.
- Most of the really famous operas were composed in the Romantic era by composers such as Verdi, Bizet, & Puccini. Oh there are plenty more, but those guys together probably have the most instantly recognizeable operas.
Most of the other types of classical I'd consider fairly niche-y and not very accessible - Baroque takes some getting used to (look for orchestras that perform on "period instruments" for an authentic sound), and some of the Modern stuff went pretty crazy on the atonality & dissonance. I won't bother covering Mozart either because he did so many works (that could be a book in itself) but Mozart is definitely essential. I'd consider Mozart's divertimentos the gateway into his genius. Maybe start with the classic Eine Kleine Nacht for Mozart, can't go wrong there.
I'd definitely also recommend listening to your local FM radio classical stations, as they can cover a very wide range in a short amount of time, and they often say what they're playing right after a piece is over.