Fundamental Line, Urlinie. The background melodic line, a stepwise descent from the Kopfton to the final tonic that spans the background of an entire movement. The Urlinie descends from the third, fifth, or octave to the tonic. Urlinie remains untranslated in the text since it is in common use among Schenkerian analysts.
The graph at the bottom of this page shows the Urlinie for Brahms's Op. 24 Variations and Fugue.