Our Improved Lattice Dynamical Model based on Generalized Pseudopotential Theory (GPT) is found to be good working in studying lattice dynamics and lattice mechanical properties of transition metals, has been used first time for the theoretical investigation of phonon frequencies of copper in off-symmetric directions. The computed results of phonon frequencies are found to be in good agreement with experimental results with average deviations 12.07 %, 6.51% and 4.76% in ν1, ν2, and ν3 respectively as well as are also in fairly agreement with other theoretical models. Our model having less number of parameters is found to be capable to reproduce phonon frequencies not only in symmetric but in off-symmetric directions without inclusion of tensor forces and modification