The tonic plays an important part in determining why music composed in a minor scale sounds different from music composed in a major scale. The answer is not obvious, when one realises that each minor scale has the same key signature and hence same set of notes as a major scale. A minor scale and major scale with the same set of notes differ only in which one of these notes is the tonic.
[more about the role of the tonic in music please]
wikipedia.org dumped 2003-03-17 with terodump