  We report a comprehensive neutron scattering study of low energy magnetic
excitations in the breathing pyrochlore helimagnetic
$\text{Cu}_2\text{OSeO}_3$. Fully documenting the four lowest energy magnetic
modes that leave the ferrimagnetic configuration of the "strong tetrahedra"
intact ($|\hbar\omega|<13$ meV), we find gapless quadratic dispersion at the
$\Gamma$ point for energies above 0.2 meV, two doublets separated by 1.6(2) meV
at the $R$ point, and a bounded continuum at the $X$ point. Our constrained
rigid spin cluster model relates these features to Dzyaloshinskii-Moriya (DM)
interactions and the incommensurate helical ground state. Combining
conventional spin wave theory with a spin cluster form-factor accurately
reproduces the measured equal time structure factor through multiple Brillouin
zones. An effective spin Hamiltonian describing the complex anisotropic
inter-cluster interactions is obtained.
