Composed between 1796 and 1798.
The sixth sonata has earned a reputation as one of Beethoven's least important sonatas. Is it because of its short duration? The truth is that any reasonably objective look will show that it really is one of the best.
The first movement explodes with innovative touches, the exuberant lyrical sonority of the first theme of the second thematic group that uses harmonies of major sevenths, the really unexpected harmonic turns; In the first part of the first movement, we have a fascinating transition from Fa to Mi, and then, without any preparation, we go from Mi to Do. A radical harmonic management for the transition of thematic groups. The development section that stubbornly avoids any connection to the exposition with the exception of a tiny ending phrase, and a recap that begins in Re, such a distant key from Fa, it seems that the tonal tension that must have been found in the development has built up precisely in the recapitulation.
The second movement continues the characteristic feature of this sonata, that of experimentation with sound. Technically it's kind of a minuet-trio, but texturally it's more of a gloomy trifle, again with beautiful textures upon the return of the minuet.
The last movement is one of the best things Beethoven has ever written; a mischievous, scampering, hyper-orchestral thing that never looks anything like a proper fugue, but sounds a lot like a fugue, and contains sudden windows of translucent, luminous light.