Songtrix

There's several uses for the Scales Track, which represents the changing key centres in a piece of music.

1.  Style generation is based on scales.  If no scale track is present, Songtrix picks a suitable default scale for each chord in the Chords track (maj => Major, m => Dorian, 7 => Mixolydian, etc).  If there is a Scales track present, it allows you more precise control over the scales used.

2.  Scales define the notes that can appear in melodies.  You can use the Scales track in a piece of music like a template for your melodies if you tick the Show Scales options in Song-Setup-Links.

The Notes To Scales tool helps you choose a scale from a collection of notes in a melody.  The Chords To Scales tool helps you choose a scale that is compatible with a chord, or a with a series of chords.

For more info on chord/scale relations, see the How Music Works tutorials.