The new critical and practical edition of Sinfonietta reflects all existing sources, including those recently discovered during the work on the edition. It is primarily based on the transcription of the score that was used to stage the premiere and then served as a print template. The transcription was subjected to the first press release, and contained the premiere manuscript orchestral voices, autograph and corrections. In principle, Sinfonietta is restored to the premiere version of 1926, when it was staged with the Czech Philharmonic Orchestra conductor Václav Talich.

However, the edition reflects some of the composer's wishes that were not taken into account at the premiere due to technical reasons and then did not make it into the edition (e.g. 12 trumpets used in the second sentence). The notes also point to the additions made by Václav Talich to the instrumentation. The use of these additions, which made it into the first edition, are thus at the discretion of the conductor. Elimination of errors and inaccuracies, which arose already in the transcription, when the copyist Václav Sedlácek inaccurately or incorrectly understood Janácek's illegible autograph, was also part of the work when preparing the edition. According to sources, the editor also added further dynamics, specified the tempo and corrected errors. In the notes, the score also makes some additions that Janácek tolerated, but it is not clear whether he completely identified himself with them (e.g. additions made by the conductor Otto Klemperer at the end).

The edition also includes possible solutions for problematic sound bottlenecks designed by Janácek's chief conductor Charles Mackerras. The edition also contains a detailed introduction, which elaborates on the genesis of the work and Janácek's views on interpretation of the composition, as evidenced by the sources (use of a military band, performance of a wind ensemble, type of instruments favoured by Janácek, etc.)