Fišer's fourth piano sonata was written between 1962-1964 and is dedicated to the memory of his friend, the pianist Antonín Jemelík, who died tragically. As a tribute to their friendship the composer incorporated into the introduction a quotation from their favorite work, Piano Sonata No. 10, Op. 70, by Alexander Scriabin. The tragedy of the death of the composer's friend pervades the emotionally intense passage of unison octaves which follows the three-bar quotation.
From a compositional point of view this work is a masterpiece of the mid-Sixties. Written as one movement, the piece is divided into numerous mutually contrasting segments which themselves are clearly grouped into two sections, exposition and development. The individual themes are introduced in the first section and thematically expanded in the second section. The motif treatment lies almost exclusively in the fragmenting or curtailing of the theme, or in the use of a combination of several themes, for the most part brief and eloquent. This compositional method, together with a clear-cut manner of execution, mainly semitonal melody and sharply contrastive dynamics, lends force and transparency to the piece.