In very low rate coding the aim is to accurately represent speech characteristics as efficiently as possible. High coding gains for the spectral features can be achieved through the use of temporal decomposition. Waveform interpolation coders accurately represent the excitation using characteristic waveforms (CWs) extracted at a constant rate. In this paper, the two approaches are combined into a very low rate coder operating at around 1 kbps. It is shown that the evolution of the excitation is related to the evolution of the speech spectrum. To minimise bit rates, the transmission of CWs is adapted to the spectral parameter evolution using the parameters derived from temporal decomposition of the spectral parameters.