Music Man

I'd start with the early and work your way forward. Here are a few recommendations to get you started:

Baroque era:

Johann Sebastian Bach--The six "Brandenburg concertos"
Johann Pachelbel--"Canon in D"

Classical era:

Wolfgang Amadeus Mozart--Symphonies #40 and #41
Franz Josef Haydn--"The Horn Signal" (Symphony #31)

Transitional period between the Classical and Romantic eras :

Ludwig van Beethoven--Symphonies #5 and #9
Franz Schubert--"The Great" (Symphony #9)

Romantic era:

Johannes Brahms--Symphony #4
Johann Strauss II--The Blue Danube

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"Paranoid is just like an anchor. It really secures everything about the metal movement in one record. It's all there: the riffs, the vocal performance of Ozzy, the song titles, what the lyrics are about. It's just a classic defining moment."

--Rob Halford of Judas Priest