the opening largo of bwv 1017 in time is a siciliano, a binary dance-form widely used in the early eighteenth century. in the minor key it was associated with a mood of melancholy or even pathos. the elegiac melodic line and ornamentation are entirely suited to the violin. as numerous commentators have pointed out, with its affecting anapaests, the compositional style and impassioned tone resemble those of the obbligato violin solo in the celebrated alto aria "erbarme dich" from bach's st. matthew passion. the harpsichord supplies a continuo-like accompaniment. there are arpeggiated semiquaver figures in the harpsichord right hand, while the quavers in the left hand—with their french "tenue" slurs gradually descending in steps—provide a rhythmic pulse gently driving the movement forward, almost like an ostinato bass.