From The Art and Popular Culture Encyclopedia
Mahler was best known during his own lifetime as one of the leading orchestral and operatic conductors of the day. He has since come to be acknowledged as among the most important post-romantic composers. With the exceptions of an early piano quartet and Totenfeier, the original tone-poem version of the first movement of the second symphony, Mahler's entire output consists of only two genres: symphony and song. Besides the nine completed numbered symphonies, his principal works are the song cycles Lieder eines fahrenden Gesellen (usually rendered as 'Songs of a Wayfarer', but literally 'Songs of a Travelling Journeyman') and Kindertotenlieder ('Songs on the Death of Children'), and the synthesis of symphony and song cycle that is Das Lied von der Erde ('The Song of the Earth').
Des Knaben Wunderhorn