The harmonic plus noise model (HNM) is widely used for spectral modeling of mixed harmonic/noise speech sounds. In this paper, we present an analysis/synthesis system based on a long-term two-band HNM. "Long-term" means that the time-trajectories of the HNM parameters are modeled using "smooth" (discrete cosine) functions depending on a small set of parameters. The goal is to capture and exploit the long-term correlation of spectral components on time segments of up to several hundreds of ms. The proposed long-term HNM enables joint compact representation of signals (thus a potential for low bit-rate coding) and easy signal transformation (e.g. time stretching) directly from the long-term parameters. Experiments show that it can be compared favourably with the short-term version in terms of parameter rates and signal quality.