[1] Properly speaking, "form" refers to the molecular constitution of music, to the ways in which relations of pitch and rhythm are manipulated in melody and harmony; "structure" to the molar constitution of music, the subsequent grouping of the melodies into complete pieces. The difference between a sonata, a fugue, and a nocturne is a difference of structure; the difference between a good melody and a bad one is a difference of form.

[2] La Revue Philosophique, Vol. LII.