Заголовок: Kadenz zum Klavierkonzert op. 15
The Concerto #1 in C actually postdates Concerto # 2 in Bb. However, Beethoven was apparently working on the concerto in C as early as 1795. During 1795 and through the next 3 years, Beethoven took up the problem of a cadenza for the 1st movement on several occasions - little overlap among this work, nor is there much overlap with the 3 cadenzas which Beethoven wrote in 1809 (most likely for Archduke Rudolph's use).
The fragments come in 4 discrete chunks. (Sources: 1) Fischoff Miscellany, page 30 (Berlin Staatsbibliothek, transcribed by Douglas Johnson) (1795); 2) Kafka Miscellany page 72 (British Museum, transcribed by Joseph Kerman, et al.) (1795-99); 3) Kafka Miscellany page 138 (Ibid.) (1796-98); and 4) Grasnick Sketchbook I page 2 (Berlin Staatsbibliothek, transcribed by Douglas Johnson) (mid-1798). (This order may be incorrect; the only thing that seems certain is that fragment 1 is not contemporaneous with fragment 4.
The 2nd of these cadenzas starts with a striking harmonic idea, which shows that Beethoven was sometimes more adventurous in his sketches than in his finished works: both left and right hands do have triads, which behave in a contrapuntal way. This results in dissonating chords of 6 different notes on the 1st counts of the opening phrase; a boldness worthy of the Eroica! After a middle section, derived from bars 216-224 and 431-439 of the 1st movement, there follows a light-hearted 2-part counterpoint, worked out as a sequence in the manner of J.S.Bach.