  We examine zero-temperature one-particle spectral functions for the
one-dimensional two-band spinless fermions with different velocities and
general forward-scattering interactions. By using the bosonization technique
and diagonalizing the model to two Tomonaga-Luttinger-liquid Hamiltonians, we
obtain general expressions for the spectral functions which are given in terms
of the Appell hypergeometric functions. For the case of identical two-band
fermions, corresponding to the SU(2) symmetric spin-1/2 fermions with repulsive
interactions,the spectral functions can be expressed in terms of the Gauss
hypergeometric functions and are shown to recover the double-peak structure
suggesting the well-known "spin-charge" separation. By tuning the difference in
velocities for the two-band fermions, we clarify the crossover in spectral
functions from the "spin-charge" separation to the decoupled fermions. We
discuss the relevance of our results to the spin-1/2 Hubbard model under a
magnetic field which can be mapped onto two-band spinless fermions.
