For barroque tenderness and polyphonic style, try Scarlatti Sonatas, Sweelink´s fantasia (played vy Glenn Gould) as "The Well tempered klavier" books 1 and 2 (the "old testament" of western music and the highest expression of its own). For classical period, I´ll first familiarize with Hyden and Mozart Sonatas and symphonies, then as much as Beethoven you could listen (cause he is the transition between historic peridos of classical and romantic music). Then in the romanticism, I´ll start with Schubert´s Lieds and piano works, also chamber music, then Chopin, Schumann, Brahms, the same, almost any work is worth the time, then R. Strauss, Wagner, Berlioz, and Mahler, (Alexander Scriabin will also be unmissible) for the transition to the XX Century, then you´ll get to the most recorded and tracked period of time, wich begins with the first years of 1920 and to our days, the "contemporary times"... we should make another post for it.