dvard Grieg published his Lyric Pieces (Lyriske stykker) in ten volumes, starting in 1867 with Op. 12 and finishing in 1901 with Op. 71. The sixth volume, written in 1890-93, and published in 1893, consists of 6 pieces, named Svundne dager (Vanished days), Gade, Illusjon (Illusion), Geheimniss (Secret), Sie tanzt (She dances), and Heimweh (Homesickness). The 10-book collection includes several of his best known pieces, such as Wedding Day at Troldhaugen (Bryllupsdag på Troldhaugen), To Spring (Til våren), March of the Trolls (Trolltog), and Butterfly (Sommerfugl). Grieg favored the theme he used on the very first piece of the set, Arietta. In fact he even usedf it to complete the piece by reworking it as a humorous waltz for the last piece of Op. 71. Even though the original publishing was made in several volumes, some editors treat the Lyric Pieces as a single set of works, numbering the 66 pieces as one single list.