A high-temperature and a weak-nonlinearity (low-temperature) semiclassical expansion are developed for computing two-dimensional vibrational Raman spectroscopies, and applied to an exactly solvable Brownian-oscillator model. The origin of photon echoes is discussed using phase-space-wave-packets. Impulsive and semi-impulsive echoes are shown to satisfy different phase-matching conditions, and are generated in different directions.