We describe the rationale for Multi-site Continuous Spectroscopy for the
study of asteroseismology, stellar surface structures, instabilities and
environments. We give some highlights of results obtained in the frame of
previous world wide MUSICOS campaigns. We also describe specific results
obtained with the recently commissioned ESA-MUSICOS spectrograph at the 2.5 m
Isaac Newton Telescope at La Palma. Finally, we present ways for the
stellar and interstellar community to use it, and to participate to future
observing campaigns.