The Digital Archives of the Beethoven-Haus contain over 5000 online facsimiles of music manuscripts, sketches, first editions, letters, and photographs, accompanied by audio files, bibliographies, and historical background.
A comprehensive list of Beethoven manuscripts in various libraries that are available online, arranged by opus number.
Ira F. Brilliant Center for Beethoven Studies digital library
They have manuscripts, first editions, portraits and other art works, etc. This website also offers a bibliography of works about Beethoven in many languages.
Only one of our two letters is currently available online, as part of an exhibit. (Scroll down to see it.) From the Miscellaneous Letters and Documents File, Misc. Ms. 372, Music Library Special Collections.
The Beethoven-Haus in Bonn (Beethoven's home town) has an excellent page that includes Beethoven's original manuscript for the Pastorale Symphony, some of his sketches for it, and a copyist's manuscript (much easier to read!) with Beethoven's corrections. It also has Beethoven's letters pertaining to the symphony, and even works of art inspired by Beethoven and the Pastorale Symphony.
Facsimile edition from the Autograph BH 64 in the Beethoven-Haus Bonn. A commentary in German by Sieghard Brandenburg follows the score, with an English translation by J. Bradford Robinson. Facsimile edition published in 2000.
Call Number: Ma21 Y11 B39 LM4672c (Music Library Special Collections, housed at LSF)
Publication Date: unpublished manuscript, [1817]
1 manuscript score ([54] pages), in the hand of Auguste Eberhard Müller (1767-1817). The manuscript later belonged to Christoph H. Rinck (1770-1846), whose library was purchased by Lowell Mason (1792-1872) and later bequeathed to the Yale Library.