From Classicist to Romanticist--in one lifespan Part IA
Of course, it's Beethoven's life! These examples that may show the tremendous change Beethoven made in his own music--and in the development of classical music generally.
Item 1 is the first movement of the sonata in c minor, Op.10, No.1. (By convention, references to minor keys use lowercase letters.) The three sonatas in Opus 10 were published in 1798; I don't know how much earlier they were written.
Item 2 is the first movement of the another sonata in c minor, Op.13 (a.k.a. the Pathétique). This sonata was written around 1798. The Pathétique is often thought of as the first modern piano sonata.
I don't know if you'll hear a tremendous difference between them or not. One thing to notice is Beethoven's use of dissonance in the Pathétique. Composers have always used chords that sound wrong (using one wrong note to create the dissonance) and then followed them with a single note or simpler chord containing the right note (this is called resolving the chord) as a neat way to build up tension. The listener may not be conscious of what's happening, but his ears are cringing in anguish until they get relief from the dissonance. Anyway, though the earliest composers knew perfectly well how to do this, Beethoven made it a regular feature of his works, and dissonance thereafter became a major way for composers to work directly with the listener's emotions. In the Pathétique, you'll hear some pioneering examples of the technique in the slow introduction. Dah, dah dah dah arrrrrgh AHHHHH, dah, dah dah dah arrrgh AHHHHH, etc.! More modern music is so much more dissonant, actually, that you might not hear the dissonance--it's comparatively tame. If you heard the chord spelled out slowly on the piano, though, you'd certainly detect the wrong note!
Item 3 is the first movement of Beethoven's piano concerto in B-flat, Op. 19. Although this is called his Piano Concerto No.2, it was written earlier than #1 (Beethoven performed it in 1795, but after he completed the one known as #1 in 1797, he revised #2) and is the closest to Mozartian of his concerti.
Item 4 is most of the first movement of one of the great piano concerti, Beethoven's concerto no.5 in E-flat, Op.73 (a.k.a. The Emperour). This is Beethoven's last piano concerto. It was first performed in 1809, and is pure romantic Beethoven.
There are (as somewhere in the miscellaneous notes I'm putting together I've said before) some 6 or 7 piano concerti that EVERY pianist and EVERY concert-goer knows. The Emperour is the earliest of them. (There's an odd little movie called The Competition with Lee Remick and a lot of unknowns. It's a piano competition with the finalists coming down to a boy and a girl who, well, you know. The movie's odd because there's quite a lot of unexcerpted music in it. Anyway, the boy enters with The Emperour.)
The best of Beethoven
Of Beethoven's nine symphonies, the memorable ones are No.3 (the Eroica), No.5 (for its opening), No.6 (the Pegasi loved it in Fantasia), No.7 (for its wonderful 2nd movement), and No.9 (for the choral Ode to Joy in it).
The Eroica is historically interesting. Beethoven was very interested in politics and a great champion of democracy. When Napoleon first took power, he seemed a champion of the people, and Beethoven enthusiastically dedicated his third symphony to Napoleon. When Napoleon crowned himself emperour, Beethoven erased the title page and re-dedicated it to the memory of a hero.
Musically, the Eroica is significant for the way it mirrors the Age of Revolution in which it was written. It is, though, the weakest of the familiar symphonies, and since I now know how little time we have, well, the historical note is all you'll get.
Ditto the lovely 6th symphony (a.k.a. The Pastoral). If you've seen Fantasia, you've heard it.
Item 1 is the first movement of the very familiar 5th symphony (Op.67 in c minor). Anyone who's heard the Edward R. Murrow broadcasts during the London blitz knows the opening!
Item 2 is an illustrative example stolen (with modification) from Leonard Bernstein's T.V. broadcasts. People who don't like modern music complain that modern music doesn't have a melody. People like melodies, even if trivial.
(ex. from piano).
Bernstein would sit at the piano and play one note over and over again. Daah, dah dah daah daah (ex. from piano). Then he'd suggest that as melodies go, this thing left a lot to be desired. You can vary it a bit (ex. from piano), but "Comin Through the Rye" still has a lot more going for it! There's not much "Johnny One-Note" can do with (exx. from piano and from orchestra).
Item 3 is the 2nd movement of his 7th symphony (Op. 92 in A).
Warning! After a loudish chord, the music gets very soft and builds. If you can hear it at all, don't adjust your volume!
The Best of Beethoven and Other Stuff I
Ask a hundred concertgoers to name the 100 "must know" works, and you'll get a hundred different lists. Two of the items here (Leonore 3 and the ninth symphony), though, will be on all lists.
Item 1 is the Overture known as Leonore No.3, Op.72a
Beethoven wrote an opera, called Fidelio. It is occasionally performed, but Beethoven's standing in music is not the result of his work in opera! He did write four overtures for Fidelio, named Fidelio (the final version) and (after the main character) Leonore 1, Leonore 2, and Leonore 3. Fidelio itself might not be Beethoven at his greatest, but Leonore 3....
Item 2 is Wellington's Victory or the Battle of Vittoria, Op.91
This isn't Beethoven's best, but it was immensely popular in its time. "The Bear Went Over the Mountain" is actually a French tune, "Malbrouck s'en va-t'en guerre", which Beethoven uses in the first part (the battle) to fight Wellington's "Rule Britannia". And as the French get creamed, he repeats the tune in a minor key. (Tchaikovsky's 1812 Overture used drums to suggest cannon, and modern recordings sometimes use real cannon. Same here.)
The second part "The Victory Symphony" was in great demand in its day and published in several arrangements (including one for brass band!).
Beethoven, the lover of democracy, celebrated any victory over Napoleon (and this one promised to bring in much needed cash!). He had a special love for England--"Rule Britannia" is the subject of an earlier (and quite nice) set of piano variations. Another set of variations was written on another "English Tune", which sounds suspiciously like "God Save the King"!
Item 3 is the song "Bundeslied", Op.122
"Bundeslied" is an uncharacteristically chipper little setting of Goethe's poem "Fellowship". I like it, and had wanted to use it somewhere. It's here, though, to break up the orchestral music. If you get distracted, you might not catch the breaks between items. If you hear a bouncy little choral number, you're here.

 
Bundeslied ("Fellowship")
 
Johann Wolfgang von Goethe

 
In every merry hour, when flushed with love and wine,
We'll sing this song together, in fellowship divine.
The God who brought us hither will keep us closely knit.
Renew our flame of friendship, for he has kindled it.
Then glow today with happiness, let all hearts beat as one,
With joy anew drink down this glass of your true wine, come on!
Now raise your glasses firmly, embrace your fellow men,
New meetings of our company make old ones new again.
Who lives within our circle, and finds no joy in it?
Enjoy its sense of freedom and real fellowship!
Let hearts then cleave together, for ever and a day,
No pettiness shall sunder our company so gay!
A noble God has blessed us with free and easy ways
And whate'er befalls us renews our happy days.
No moody disagreement shall yet our pleasure mar,
Our hearts shall beat the freer, no ceremony jar.
Each step will bring us further on life's tempestuous way;
Our gaze shall rise with gladness to meet the coming day.
We fear not, no we fear not: though earthly empire ends--
We're fellows now forever, for friendship all transcends.
Item 4 is the first movement of Beethoven's Ninth Symphony (Op.125 in d minor, the "Choral Symphony")
The symphony is an hour long and won't fit in one segment. Beethoven indicated that he wanted the third and fourth movements played without a break, so I broke it here.
Warning! The ninth begins with a (much imitated) "misty" opening played very softly, and gets loud REAL FAST. If you can hear the beginning at all, don't turn your volume up!

 
The Bottom of the Ninth
The one item is the rest of the ninth symphony--the 2nd, 3rd, and 4th movements. You may recognize the beginning of the 2nd movement, which tends to get used to introduce T.V. specials, etc.
The Final Movement is a setting of Friedrich von Schiller's poem "Ode to Joy".
The "Ode to Joy" is a hymn in praise of the brotherhood of man, a poem Beethoven fell in love with in his youth and had always intended to set to music. In this movement you hear a very German-burgher-type chorus, a popular march (done in what was called the "Turkish" style), a couple of rustic dances, all feeding in to the great chorale--it's almost like a procession of people from all walks of life. And at the end there's a quiet moment of contemplation before a rather frenzied ending (?caps thrown into the air).
The audience was wildly enthusiastic at its premiere performance. No one describes the ninth without mentioning the moment at the conclusion of this performance, which Beethoven conducted, when one of the singers had to turn him around to face the audience: the now-deaf composer could not hear the applause. He never heard his own realization of his boyhood dream.

 
Ode to Joy
Friedrich von Schiller
translator unknown

O friends, no more these sounds!
Let us sing more cheerful songs, more full of joy!
Joy, bright spark of divinity,
Daughter of Elysium,
Fire-inspired we tread
Thy sanctuary.
Thy magic power re-unites
All that custom has divided,
All men become brothers
Under the sway of thy gentle wings.
Whoever has created
An abiding friendship,
Or has won
A true and loving wife,
All who can call at least one soul theirs,
Join in our song of praise;
But any who cannot must creep tearfully
Away from our circle.
All creatures drink of joy
At nature's breast.
Just and unjust
Alike taste of her gift;
She gave us kisses and the fruit of the vine,
A tried friend to the end.
Even the worm can feel contentment,
And the cherub stands before God!
Gladly, like the heavenly bodies
Which He set on their courses
Through the splendour of the firmament;
Thus, brothers, you should run your race,
As a hero going to conquest.
You millions, I embrace you.
This kiss is for all the world!
Brothers, above the starry canopy
There must dwell a loving Father.
Do you fall in worship, you millions?
World, do you know your Creator?
Seek Him in the heavens,
Above the stars must He dwell.
Haydn wrote over a hundred symphonies, and in part was able to do so because the symphony in his day (he taught both Beethoven and Mozart, so "his day" isn't so remote from them) was a much lighter-weight composition. It was, for one thing, shorter. And, though this is the kind of thing that's hard to define, it was a much shallower work.
Mozart wrote 41 symphonies, in part because he was Mozart and in part because many of his symphonies are of the shorter, lighter-weight type. Still, the modern, large-scale symphony starts with Mozart.
It comes into its own with Beethoven, though. His nine symphonies (a tenth was unfinished at his death) are the models for the modern symphony. (So is the number. Bruckner, for one, was superstitious about his own ninth symphony--he knew he would not write a tenth, because he knew he would never write more than did Beethoven.) And of the nine, the "Choral Symphony" opened the way to mergers of hymns (with or without choirs) and orchestras in these massive works. Bruckner's symphonies were pretty much all inspired by the ninth. (Though Bruckner merged religious rather than humanist hymns with music.) Mahler wrote huge works for choir and orchestra (his eighth symphony, the "Symphony of a Thousand", actually calls for three choirs and soloists!).
Gee, and it all starts here!