This piece is called "Toccata No. 1" because multiple manuscript sources are inscribed as such, and it might also be because it was the earliest of the seven pieces to be published, in 1801.

The work comprises an introductory toccata section, a fugal section titled Thema (or Presto in some sources), a slow transitional section connecting short motives, another fugal section, and it concludes with a toccata-like coda. If one follows the double bar lines, it is a four-part structure, but the final coda brings it closer to the traditional T-F-T-F-T form.

However, in the initial toccata section, the texture changes abruptly after the rest in measure 15. Furthermore, the preceding introductory section itself juxtaposes diverse elements: it begins in a pedal-bass style, rushes down scales, proceeds for a while with sigh motives, and then again intersperses scale passages.

The fugue subject is already prepared in the latter half of the toccata section. However, the beginning of the first fugal section, designated as Thema, does not feature a typical subject presentation and a response at the fifth; instead, it is merely imitated loosely at the octave, resulting in a generally free fugal writing throughout. This impressive subject appears everywhere, with its rhythmic shape reconfigured and variations resembling inversion or retrograde added, and subsequently provides material for the transitional section.

The second fugue also begins with an octave imitation but possesses a clear countersubject. The development of this fugue is more intricately structured compared to the initial Thema.

The subject is not entirely lost even when entering the final arpeggiated coda. Here, the crisp rhythm dissolves into the flow of sequential progressions, eventually emerging in fragments, heightening the anticipation for the subject's return. Finally, in the last three measures, the subject is restated, bringing the piece to a close.

This work is replete with common idioms of organ music from that period (e.g., pedal bass, scale passages spanning the full keyboard width, arpeggiated sequential progressions), and one might occasionally perceive a slight awkwardness at their junctures. However, what unifies these elements is the rhythmic figure clearly presented in the Thema. This is the only one among the seven pieces that exhibits unification through a motive.