63, is a set of 49 short piano pieces by French composer Charles-Valentin Alkan and published in 1861.
Book 4 ends with an extra, unnumbered, piece, Laus Deo, in C major.
Four pianists have recorded the set in its entirety: Laurent Martin, Osamu Nakamura (now Osamu Kanazawa), Steven Osborne, and Yui Morishita (twice).
39 set of etudes in all the minor keys, these 49 pieces do not focus mainly on virtuosity and transcendentalism and instead contain more of Alkan's sentimental and evocative writing.
The 45th piece, Les Diablotins, features wrenched cluster chords and the 48th piece, En Songe, is a dreamy and quiet piece all except for the very final chord, which is a sudden F major chord with the dynamic ff.