The Symphony No. 7 by Gustav Mahler was written in 1904–05, with repeated revisions to the scoring. This five movement piece is sometimes referred to by the title Song of the Night (German: Lied der Nacht), which Mahler never knew. Although the symphony is often described as being in the key of E minor, its tonal scheme is more complicated. The symphony's first movement moves from B minor (introduction) to E minor, and the work ends with a rondofinale in C major. Thus, as Dika Newlin has pointed out, "in this symphony Mahler returns to the ideal of 'progressive tonality' which he had abandoned in the Sixth". The complexity of the work's tonal scheme was analysed in terms of "interlocking structures" by Graham George.
The harmonic and stylistic structure of the piece may be viewed as a depiction of the journey from dusk till dawn. The piece evolves from uncertain and hesitant beginnings to an unequivocal C major finale, with its echoes of Wagner's Die Meistersinger von Nürnberg: indeed, at the premiere the overture to this opera was performed after the symphony.
This journey from night to day proceeds via an extraordinary third movement scherzo, marked schattenhaft (shadowy), which may have been what prompted Arnold Schoenberg to become a particular champion of the work. The abundance of themes based upon the interval of a fourth has parallels with the First Chamber Symphony.
The piece has several motifs in common with the Symphony No. 6, notably the juxtaposition of major with minor chords, the march figure of the first movement, and the use of cowbells within certain pastoral episodes.