"I think dispersed harmony is created throughout a piece of music where it is composed as most Sacred Harp composers do -- as horizontal strands rather than vertical chords. Each part is written so as to make it a singable tune of its own and this leads to 'open chords'. (Open chords being defined as chords in which another note can be inserted between the upper voices.) Sacred Harp composers move from 'open' to 'closed' chords without regard to where the change takes place in the phrase. Add to this the frequent crossing of voices throughout the composition, especially between treble and tenor, and we have two essential points in the style known as 'dispersed harmony'." -- Raymond Hamrick (in a letter to Hugh McGraw, November 1981)
I'm going to add this to my dispersed harmony definitions page, but wanted to post it here so folks might notice it. I thought it was interesting that Hugh and Raymond were discussing the correct meaning of 'dispersed harmony' as late as 1981.