A time multiplex arrangement for presenting multiple samples to a single channel of NMR excitation/data acquisition includes means for rapid exchange of physical position between plural samples or sample portions from the measurement volume of the NMR instrument while said samples remain in a substantially the same homogeneous magnetic field. While a delay is imposed upon time evolution or relaxation of an NMR excited sample outside the sensitive volume of an RF resonator, another sample is actively excited within said RF resonator whereby the steps of NMR measurement are overlapped between at least two samples.