The Theme as a Determinant of the Structural Elements and Sections. An Analytical Approach of the Form in Invention no. 4 in d minor of J. S. Bach
This article argues that one of the purposes of the 15 two-part inventions of J. S. Bach is to show, as Bach himself put it in his manuscript of 1723, “a clear method […] not only of arriving at good original ideas (inventions), but also of developing them satisfactorily, i.e. of composing”. It is also argued that “satisfactory development” is the finding of those procedures of composition, through which the initial thematic material is elaborated in the best possible way.The analysis of the invention no. 4 in d minor provides an example that (a) the non exact recapitulation of the initial theme, as it is exposed in mm. 1-6, in any part of the piece, even during its final recapitulation in the initial tonality, (b) the impossibility for the theme to be exposed in any major tonality, (c) the transitional quality of the theme, (d) the continuous renewal of the harmonic investment of the three motives (al, a2, b), and (e) the overlapping of the subsections of the second section of the invention (mm. 26-52), are the result of the “satisfactory development” of the initial thematic idea of this invention.