In Kathleen Schlesinger's theory, a portion of the subharmonic series between a Modal Determinant and its upper octave is a Modal Octave or Harmonia.
See also: Kathleen Schlesinger, "The Greek Aulos" 
The tonalsoft.com website is almost entirely the work of one person: me, Joe Monzo. Please reward me for my knowledge and effort by choosing your preferred level of financial support. Thank you.