  We present a picture of the matter bispectrum in a novel "interferometric"
basis designed to highlight interference of the baryon acoustic oscillations
(BAO) in the power spectra composing it. Triangles where constructive
interference amplifies BAO provide stronger cosmic distance constraints than
triangles with destructive interference. We show that the amplitude of the BAO
feature in the full cyclically summed bispectrum can be decomposed into simpler
contributions from single terms or pairs of terms in the perturbation theory
bispectrum, and that across large swathes of our parameter space the full BAO
amplitude is described well by the amplitude of BAO in a single term. The
dominant term is determined largely by the $F^{(2)}$ kernel of Eulerian
standard perturbation theory. We present a simple physical picture of the BAO
amplitude in each term; the BAO signal is strongest in triangle configurations
where two wavenumbers differ by a multiple of the BAO fundamental wavelength.
