The generic band structure of high-TC copper oxides is simulated by the nearly-free-electron model in two dimensions with parameters from ab-initio linear muffin-tin orbital calculations. Interaction between phonons and spin waves will cause potential modulations, and pseudogaps and the strength of the modulations, the wavelengths, and the doping are all related. A Fermi-surface “arc” is found for dynamic spin and phonon waves. The confinement of superconductivity between two limiting dopings can be a result of competition with the pseudogap at low doping and weak coupling at high doping.