We investigate soliton solutions of the Toda hierarchy on a quasi-periodic
finite-gap background by means of the double commutation method and the inverse
scattering transform. In particular, we compute the phase shift caused by a
soliton on a quasi-periodic finite-gap background. Furthermore, we consider
short range perturbations via scattering theory. We give a full description of
the effect of the double commutation method on the scattering data and
establish the inverse scattering transform in this setting.Comment: 16 page