Mendelssohn's "Allegro Brillant" Op. 92 of 1841 is a large piece for piano 4 hands. It is in concerto-allegro form including, in effect, a cadenza (bars 274-373). Its second theme is a lyrical highlight. The excerpt shown below is played by the secondo player alone but is rewritten on 3 staves, showing that it is a "Song Without Words" in all but name.

That theme resembles Schubert's Frühlingssehnsucht (Spring Longing) D957/3 of 1828. Mendelssohn's is transposed up a semitone for the comparison. Although Mendelssohn very possibly knew the Schubert song, the borrowing might have been subconscious rather than deliberate. The close resemblance suggests the kind of meaning possible for Mendelssohn's wordless theme: the Schubert/Rellstab text means "whispering breezes blowing so gently", continuing with the repetition of the phrase "exuding the fragrance of flowers". The romantic intention is confirmed by the theme's continuation in the cadenza, where the players' arms symbolically interlock (bars 350-357).

If the meaning is of that kind, why are the tempo indications of both works fast? I believe it is because both metres, or pulses, are essentially 12/8, combining two notated bars (the barlines are only for visual convenience). Thus each notated bar passes in a short time, allowing the "real" 12/8 bars to pass at a moderate tempo.

One difference between the two melodies is Schubert's low fourth note: an A could have been used, but the F lends a distictive quality. It is more likely the contexts, though, which explain why Schubert's is famous, Mendelssohn's little-known. Closer comparison reveals features of the two musical personalities, to be pursued another time.

Schubert was incomparable in songs with words, where the pianist's hands are both free for the accompaniment. In songs without words (with various names such as Moment Musical No. 2, No. 6) Schubert's full right-hand textures give a different effect by comparison with Mendelssohn's wonderfully light touch.