In writings about Johannes Brahms's Trio for violin, horn, and pianoforte in Eb major op.40, it has been frequently remarked that a twobar major-key phrase toward the end of the subdued third movement anticipates the lusty opening idea of the Finale.' But the correspondence between the two passages extends beyond the initial two bars of the theme (exx.i & 2, segment 1) to encompass also the following two bars (exx.i & 2, segment 2), which begin and end with rising motion from C to G, directly or in outline. Exx.i & 2 show the two passages, with their corresponding notes marked by Xs. Furthermore, the second element of this idea had been heard earlier in the third movement, specifically as the brief theme of the second key area (beginning in bar 19), just before the onset of the development section (compare ex.3 with ex.2, including the Xs within parentheses). At the beginning of the recapitulation in the third movement (bar 43), this second element is combined with the original first theme, revealing that its seed had been germinating since at least the beginning of the movement.
It should have been obvious, but it has never been remarked, that each of these two thematic elements is found earlier in Brahms's Trio. The first element - the motto of the Finale - is slightly decorated and metrically displaced - in typical Brahmsian fashion - but nevertheless unequivocally recognisable in the second half-phrase of the second movement, as shown by the Xs in ex.4. And the haunting opening theme of the first movement can easily be seen as a major-key adumbration of the second element, as shown by the Xs in ex.5. (The fifth Bb-F is associated with the minor sixth, Gb, a bit later, in bars 16-20.)
Given the intensity with which these themes are developed in their respective movements, it is not a great exaggeration to say that the majority of the motivic material of the entire op.40 Trio is derived from the theme that is heard in its clearest and simplest form at the beginning of the Finale.
Max Kalbeck, Brahms's close friend and early biographer, asserted that the theme of the op.40 Finale was derived from the German folksong Don in den Weiden steht ein Haus, whose beginning is given as ex.6.2 It does not require remarkable musical insight, however, to see that the folksong and the theme do not match up particularly well. One is major, the other minor. And the highly characteristic omission of the fourth scale-degree, suggesting a pentatonic collection, and the prompt return to the tonic in Brahms's theme are not found in this folksong. And from the other side, the neighbour-note motion between D and Eb that flavour this folksong is not at all present in Brahms's Finale theme.
Even less convincing is Kalbeck's reference to the chorale Wer nur den liehen Gott läßt walten (ex.7) as a source of Brahms's melodic material in op.40. Brahms did know Dort in den Weiden steht ein Haus: it is found in the anthology of German folksongs compiled by Maßmann, Zuccalmaglio, and Kretzschmer that he owned,5 and he arranged the song at least four times.4 Paging further through the Maßmann-Zuccalmaglio-Kretzschmer anthology, however, one eventually comes to another folksong that is an exact match and must have been Brahms's source for the first theme of the Finale: Es soll sich ja keiner mit der Liebe abgeben, which is given in its entirety as ex. 8.
What is striking here, of course, is that the opening of Brahms's Finale is identical to the first half of the folksong in interval structure, rhythm, metrical orientation, and even note repetition. Only the passing note at the end of bar 2 in the folksong is omitted in Brahms's theme. Furthermore, the downward movement through scale degrees 8-7-6, which sets up the second element of Brahms's theme, is found at the beginning of the second half of the folksong (bars 5-6). I think that there can be no doubt that Es soil sich ja keiner mit der Liebe abgeben …